Subject: Re: [PATCH 3/3] drm/bridge: Add NWL MIPI DSI host controller support

From: Laurent Pinchart <[email-masked]>
Date: Sat, 27 Jul 2019 05:47:00 +0300

Hello Guido,

Thank you for the patch.

On Wed, Jul 24, 2019 at 05:52:26PM +0200, Guido Günther wrote:
> This adds initial support for the NWL MIPI DSI Host controller found on
> i.MX8 SoCs.
> 
> It adds support for the i.MX8MQ but the same IP can be found on
> e.g. the i.MX8QXP.
> 
> It has been tested on the Librem 5 devkit using mxsfb.
> 
> Signed-off-by: Guido Günther <[email-masked]>
> Co-developed-by: Robert Chiras <[email-masked]>
> ---
>  drivers/gpu/drm/bridge/Kconfig           |   2 +
>  drivers/gpu/drm/bridge/Makefile          |   1 +
>  drivers/gpu/drm/bridge/imx-nwl/Kconfig   |  15 +
>  drivers/gpu/drm/bridge/imx-nwl/Makefile  |   2 +
>  drivers/gpu/drm/bridge/imx-nwl/nwl-drv.c | 529 ++++++++++++++++
>  drivers/gpu/drm/bridge/imx-nwl/nwl-drv.h |  72 +++
>  drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.c | 745 +++++++++++++++++++++++
>  drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.h | 111 ++++
>  8 files changed, 1477 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/Kconfig
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/Makefile
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/nwl-drv.c
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/nwl-drv.h
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.c
>  create mode 100644 drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.h
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index a6eec908c43e..38c3145a7e57 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -152,6 +152,8 @@ source "drivers/gpu/drm/bridge/analogix/Kconfig"
>  
>  source "drivers/gpu/drm/bridge/adv7511/Kconfig"
>  
> +source "drivers/gpu/drm/bridge/imx-nwl/Kconfig"
> +

As this doesn't seem to be an i.MX-specific IP, I wouldn't use the name
imx in file names or in the code, at least in the parts that are not
NXP-specific.

>  source "drivers/gpu/drm/bridge/synopsys/Kconfig"
>  
>  endmenu
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 4934fcf5a6f8..904a9eb3a20a 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -16,4 +16,5 @@ obj-$(CONFIG_DRM_ANALOGIX_DP) += analogix/
>  obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
>  obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
>  obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
> +obj-y += imx-nwl/
>  obj-y += synopsys/
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/Kconfig b/drivers/gpu/drm/bridge/imx-nwl/Kconfig
> new file mode 100644
> index 000000000000..822dba1b380a
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/Kconfig
> @@ -0,0 +1,15 @@
> +config DRM_IMX_NWL_DSI
> +	tristate "Support for Northwest Logic MIPI DSI Host controller"
> +	depends on DRM && (ARCH_MXC || ARCH_MULTIPLATFORM || COMPILE_TEST)
> +	depends on COMMON_CLK
> +	depends on OF && HAS_IOMEM
> +	select DRM_KMS_HELPER
> +	select DRM_MIPI_DSI
> +	select DRM_PANEL_BRIDGE
> +	select GENERIC_PHY_MIPI_DPHY
> +	select MFD_SYSCON
> +	select REGMAP_MMIO
> +	help
> +	  This enables the Northwest Logic MIPI DSI Host controller as
> +	  found on NXP's i.MX8 Processors.
> +
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/Makefile b/drivers/gpu/drm/bridge/imx-nwl/Makefile
> new file mode 100644
> index 000000000000..9fa63483da5b
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/Makefile
> @@ -0,0 +1,2 @@
> +imx-nwl-objs := nwl-drv.o nwl-dsi.o
> +obj-$(CONFIG_DRM_IMX_NWL_DSI) += imx-nwl.o
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.c b/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.c
> new file mode 100644
> index 000000000000..451f8f067c6f
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.c
> @@ -0,0 +1,529 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * i.MX8 NWL MIPI DSI host driver
> + *
> + * Copyright (C) 2017 NXP
> + * Copyright (C) 2019 Purism SPC
> + */
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_probe_helper.h>
> +#include <linux/clk-provider.h>

This doesn't seem to be needed.

> +#include <linux/clk.h>
> +#include <linux/component.h>

Same here.

> +#include <linux/gpio/consumer.h>
> +#include <linux/irq.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/mfd/syscon/imx8mq-iomuxc-gpr.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/phy/phy.h>
> +#include <linux/regmap.h>
> +#include <linux/sys_soc.h>
> +#include <video/videomode.h>
> +
> +#include "nwl-drv.h"
> +#include "nwl-dsi.h"
> +
> +#define DRV_NAME "imx-nwl-dsi"
> +
> +/* 8MQ SRC specific registers */
> +#define SRC_MIPIPHY_RCR	0x28
> +#define RESET_BYTE_N	BIT(1)
> +#define RESET_N		BIT(2)
> +#define DPI_RESET_N	BIT(3)
> +#define ESC_RESET_N	BIT(4)
> +#define PCLK_RESET_N	BIT(5)
> +
> +/* Possible clocks */
> +#define CLK_PIXEL	"pixel"
> +#define CLK_CORE	"core"
> +#define CLK_BYPASS	"bypass"
> +
> +enum imx_ext_regs {
> +	IMX_REG_CSR = BIT(1),
> +	IMX_REG_SRC = BIT(2),
> +	IMX_REG_GPR = BIT(3),
> +};
> +
> +static const struct regmap_config nwl_dsi_regmap_config = {
> +	.reg_bits = 16,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +	.max_register = IRQ_MASK2,
> +	.name = DRV_NAME,
> +};
> +
> +struct imx_nwl_platform_data {
> +	int (*poweron)(struct imx_nwl_dsi *dsi);
> +	int (*poweroff)(struct imx_nwl_dsi *dsi);
> +	u32 ext_regs; /* required external registers */
> +	struct imx_nwl_clk_config clk_config[NWL_MAX_PLATFORM_CLOCKS];
> +};
> +
> +static inline struct imx_nwl_dsi *bridge_to_dsi(struct drm_bridge *bridge)
> +{
> +	return container_of(bridge, struct imx_nwl_dsi, bridge);
> +}
> +
> +static void imx_nwl_dsi_set_clocks(struct imx_nwl_dsi *dsi, bool enable)
> +{
> +	struct device *dev = dsi->dev;
> +	const char *id;
> +	struct clk *clk;
> +	unsigned long new_rate, cur_rate;
> +	bool enabled;
> +	size_t i;
> +	int ret;
> +
> +	DRM_DEV_DEBUG_DRIVER(dev, "%sabling platform clocks",
> +			     enable ? "en" : "dis");
> +	for (i = 0; i < ARRAY_SIZE(dsi->pdata->clk_config); i++) {
> +		if (!dsi->clk_config[i].present)
> +			continue;
> +		id = dsi->clk_config[i].id;
> +		clk = dsi->clk_config[i].clk;
> +		new_rate = dsi->clk_config[i].rate;
> +		cur_rate = clk_get_rate(clk);
> +		enabled = dsi->clk_config[i].enabled;
> +
> +		/* BYPASS clk must have the same rate as PHY_REF clk */
> +		if (!strcmp(id, CLK_BYPASS))
> +			new_rate = clk_get_rate(dsi->phy_ref_clk);
> +
> +		if (enable) {
> +			if (enabled && new_rate != cur_rate)
> +				clk_disable_unprepare(clk);
> +			else if (enabled && new_rate == cur_rate)
> +				continue;
> +			if (new_rate > 0)
> +				clk_set_rate(clk, new_rate);
> +			ret = clk_prepare_enable(clk);
> +			if (ret < 0) {
> +				DRM_DEV_ERROR(dev, "Failed to enable clock %s",
> +					      id);
> +			}
> +			dsi->clk_config[i].enabled = true;
> +			cur_rate = clk_get_rate(clk);
> +			DRM_DEV_DEBUG_DRIVER(
> +				dev, "Enabled %s clk (rate: req=%lu act=%lu)\n",
> +				id, new_rate, cur_rate);
> +		} else if (enabled) {
> +			clk_disable_unprepare(clk);
> +			dsi->clk_config[i].enabled = false;
> +			DRM_DEV_DEBUG_DRIVER(dev, "Disabled %s clk\n", id);
> +		}
> +	}
> +}
> +
> +static void imx_nwl_dsi_enable(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +	int ret;
> +
> +	imx_nwl_dsi_set_clocks(dsi, true);
> +
> +	ret = dsi->pdata->poweron(dsi);
> +	if (ret < 0)
> +		DRM_DEV_ERROR(dev, "Failed to power on DSI (%d)\n", ret);
> +}
> +
> +static void imx_nwl_dsi_disable(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +
> +	if (dsi->dpms_mode != DRM_MODE_DPMS_ON)
> +		return;
> +

The DRM core should guarantee that the bridge won't be disabled twice,
so I don't think you need this check. Similarly I think the enabled flag
in the imx_nwl_clk_config structure can be removed.

> +	DRM_DEV_DEBUG_DRIVER(dev, "Disabling encoder");

Is this really needed ?

> +	dsi->pdata->poweroff(dsi);
> +	imx_nwl_dsi_set_clocks(dsi, false);
> +}
> +
> +static void imx_nwl_select_input_source(struct imx_nwl_dsi *dsi)
> +{
> +	struct device_node *remote;
> +	u32 mux_val = IMX8MQ_GPR13_MIPI_MUX_SEL;
> +
> +	remote = of_graph_get_remote_node(dsi->dev->of_node, 0, 0);
> +	if (strcmp(remote->name, "lcdif") == 0)
> +		mux_val = 0;
> +

Can't you check the remote node at probe time instead of every time the
bridge gets enabled, and program the IO mux accordingly there ?

This code is i.MX-specific, so it should be isolated in an operation in
struct imx_nwl_platform_data.

> +	DRM_DEV_INFO(dsi->dev, "Using %s as input source\n",
> +		     (mux_val) ? "DCSS" : "LCDIF");
> +	regmap_update_bits(dsi->mux_sel, IOMUXC_GPR13,
> +			   IMX8MQ_GPR13_MIPI_MUX_SEL, mux_val);
> +	of_node_put(remote);
> +}
> +
> +static void imx_nwl_dsi_bridge_disable(struct drm_bridge *bridge)
> +{
> +	struct imx_nwl_dsi *dsi = bridge_to_dsi(bridge);
> +
> +	if (dsi->dpms_mode != DRM_MODE_DPMS_ON)
> +		return;
> +
> +	nwl_dsi_disable(dsi);
> +	imx_nwl_dsi_disable(dsi);
> +	pm_runtime_put_sync(dsi->dev);

Do you need a put_sync, wouldn't a put do ?

> +	dsi->dpms_mode = DRM_MODE_DPMS_OFF;
> +}
> +
> +static bool
> +imx_nwl_dsi_bridge_mode_fixup(struct drm_bridge *bridge,
> +			      const struct drm_display_mode *mode,
> +			      struct drm_display_mode *adjusted_mode)
> +{
> +	struct imx_nwl_dsi *dsi = bridge_to_dsi(bridge);
> +	struct device *dev = dsi->dev;
> +	union phy_configure_opts new_cfg;
> +	unsigned long phy_ref_rate;
> +	int ret;
> +
> +	ret = nwl_dsi_get_dphy_params(dsi, adjusted_mode, &new_cfg);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * If hs clock is unchanged, we're all good - all parameters are
> +	 * derived from it atm.
> +	 */
> +	if (new_cfg.mipi_dphy.hs_clk_rate == dsi->phy_cfg.mipi_dphy.hs_clk_rate)
> +		return true;
> +
> +	phy_ref_rate = clk_get_rate(dsi->phy_ref_clk);
> +	DRM_DEV_DEBUG_DRIVER(dev, "PHY at ref rate: %lu\n", phy_ref_rate);
> +	if (ret < 0) {

This can't happen. Or are you missing a function call before the check ?

> +		DRM_DEV_ERROR(dsi->dev,
> +			      "Cannot setup PHY for mode: %ux%u @%d Hz\n",
> +			      adjusted_mode->hdisplay, adjusted_mode->vdisplay,
> +			      adjusted_mode->clock);
> +		DRM_DEV_ERROR(dsi->dev, "PHY ref clk: %lu, bit clk: %lu\n",
> +			      phy_ref_rate, new_cfg.mipi_dphy.hs_clk_rate);
> +	} else {
> +		/* Save the new desired phy config */
> +		memcpy(&dsi->phy_cfg, &new_cfg, sizeof(new_cfg));

The mode_fixup operation shall not change the device state, it can be
called multiple times when trying modes.

> +	}
> +
> +	/* LCDIF + NWL needs active high sync */
> +	adjusted_mode->flags |= (DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC);
> +	adjusted_mode->flags &= ~(DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC);
> +
> +	drm_display_mode_to_videomode(adjusted_mode, &dsi->vm);
> +	drm_mode_debug_printmodeline(adjusted_mode);
> +
> +	return ret == 0;

	return 0;

> +}
> +
> +static enum drm_mode_status
> +imx_nwl_dsi_bridge_mode_valid(struct drm_bridge *bridge,
> +			      const struct drm_display_mode *mode)
> +{
> +	struct imx_nwl_dsi *dsi = bridge_to_dsi(bridge);
> +	int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +
> +	if (bpp < 0) {
> +		DRM_DEV_ERROR(dsi->dev, "Invalid pixel format: %d\n",
> +			      dsi->format);
> +		return MODE_BAD;
> +	}

The format isn't part of the mode, so this doesn't belong here. You
should here instead check that the mode clock and other timing data
(especially the visible resolution) are within the range supported by
the device.

> +
> +	return MODE_OK;
> +}
> +
> +static void imx_nwl_dsi_bridge_pre_enable(struct drm_bridge *bridge)
> +{
> +	struct imx_nwl_dsi *dsi = bridge_to_dsi(bridge);
> +
> +	if (dsi->dpms_mode == DRM_MODE_DPMS_ON)
> +		return;
> +
> +	imx_nwl_select_input_source(dsi);
> +	pm_runtime_get_sync(dsi->dev);
> +	imx_nwl_dsi_enable(dsi);
> +	nwl_dsi_enable(dsi);
> +	dsi->dpms_mode = DRM_MODE_DPMS_ON;
> +}
> +
> +static int imx_nwl_dsi_bridge_attach(struct drm_bridge *bridge)
> +{
> +	struct imx_nwl_dsi *dsi = bridge->driver_private;
> +	struct drm_encoder *encoder = bridge->encoder;
> +
> +	if (!encoder) {
> +		DRM_DEV_ERROR(dsi->dev, "Parent encoder object not found\n");
> +		return -ENODEV;
> +	}

Can't this happen ?

> +
> +	/* Set the encoder type as caller does not know it */
> +	bridge->encoder->encoder_type = DRM_MODE_ENCODER_DSI;

The encoder type is quite meaningless and userspace should not depend on
it, so I wouldn't set it here, especially that the encoder may not
expect the bridge to override its type.

> +
> +	/* Attach the panel-bridge to the dsi bridge */
> +	return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge);
> +}
> +
> +static void imx_nwl_dsi_bridge_detach(struct drm_bridge *bridge)
> +{
> +	struct imx_nwl_dsi *dsi = bridge->driver_private;
> +
> +	drm_of_panel_bridge_remove(dsi->dev->of_node, 1, 0);

This is already done in nwl_dsi_host_detach().

> +}
> +
> +/* see dw-mipi-dsi.c */

What for ? :-)

> +static const struct drm_bridge_funcs imx_nwl_dsi_bridge_funcs = {
> +	.pre_enable	= imx_nwl_dsi_bridge_pre_enable,
> +	.disable    = imx_nwl_dsi_bridge_disable,
> +	.mode_fixup = imx_nwl_dsi_bridge_mode_fixup,
> +	.mode_valid = imx_nwl_dsi_bridge_mode_valid,
> +	.attach	    = imx_nwl_dsi_bridge_attach,
> +	.detach	    = imx_nwl_dsi_bridge_detach,
> +};
> +
> +static int imx_nwl_dsi_parse_dt(struct imx_nwl_dsi *dsi)
> +{
> +	struct device_node *np = dsi->dev->of_node;
> +	struct platform_device *pdev = to_platform_device(dsi->dev);
> +	struct resource *res;
> +	struct clk *clk;
> +	const char *clk_id;
> +	void __iomem *base;
> +	int i, ret;
> +
> +	dsi->phy = devm_phy_get(dsi->dev, "dphy");
> +	if (IS_ERR(dsi->phy)) {
> +		ret = PTR_ERR(dsi->phy);
> +		dev_err(dsi->dev, "Could not get PHY (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	/* Platform dependent clocks */
> +	memcpy(dsi->clk_config, dsi->pdata->clk_config,
> +	       sizeof(dsi->pdata->clk_config));
> +
> +	for (i = 0; i < ARRAY_SIZE(dsi->pdata->clk_config); i++) {
> +		if (!dsi->clk_config[i].present)
> +			continue;
> +
> +		clk_id = dsi->clk_config[i].id;
> +		clk = devm_clk_get(dsi->dev, clk_id);
> +		if (IS_ERR(clk)) {
> +			ret = PTR_ERR(clk);
> +			dev_err(dsi->dev, "Failed to get %s clock (%d)\n",
> +				clk_id, ret);
> +			return ret;
> +		}
> +		DRM_DEV_DEBUG_DRIVER(dsi->dev, "Setup clk %s (rate: %lu)\n",
> +				     clk_id, clk_get_rate(clk));
> +		dsi->clk_config[i].clk = clk;
> +	}
> +
> +	/* DSI clocks */
> +	clk = devm_clk_get(dsi->dev, "phy_ref");
> +	if (IS_ERR(clk)) {
> +		ret = PTR_ERR(clk);
> +		dev_err(dsi->dev, "Failed to get phy_ref clock: %d\n", ret);
> +		return ret;
> +	}
> +	dsi->phy_ref_clk = clk;
> +
> +	clk = devm_clk_get(dsi->dev, "rx_esc");
> +	if (IS_ERR(clk)) {
> +		ret = PTR_ERR(clk);
> +		dev_err(dsi->dev, "Failed to get rx_esc clock: %d\n", ret);
> +		return ret;
> +	}
> +	dsi->rx_esc_clk = clk;
> +
> +	clk = devm_clk_get(dsi->dev, "tx_esc");
> +	if (IS_ERR(clk)) {
> +		ret = PTR_ERR(clk);
> +		dev_err(dsi->dev, "Failed to get tx_esc clock: %d\n", ret);
> +		return ret;
> +	}
> +	dsi->tx_esc_clk = clk;
> +
> +	dsi->csr = syscon_regmap_lookup_by_phandle(np, "csr");
> +	if (IS_ERR(dsi->csr) && dsi->pdata->ext_regs & IMX_REG_CSR) {
> +		ret = PTR_ERR(dsi->csr);
> +		DRM_DEV_ERROR(dsi->dev, "Failed to get CSR regmap: %d\n",
> +			      ret);
> +		return ret;
> +	}

This doesn't seem to be used anywhere.

> +	dsi->reset = syscon_regmap_lookup_by_phandle(np, "src");
> +	if (IS_ERR(dsi->reset) && (dsi->pdata->ext_regs & IMX_REG_SRC)) {
> +		ret = PTR_ERR(dsi->reset);
> +		DRM_DEV_ERROR(dsi->dev, "Failed to get SRC regmap: %d\n",
> +			      ret);
> +		return ret;
> +	}

Couldn't you model a reset controller in that syscon, and use the reset
controller API here ? It would allow moving the i.MX-specific power on
and off functions from this driver, making it more generic.

> +	dsi->mux_sel = syscon_regmap_lookup_by_phandle(np, "mux-sel");
> +	if (IS_ERR(dsi->mux_sel) && (dsi->pdata->ext_regs & IMX_REG_GPR)) {
> +		ret = PTR_ERR(dsi->mux_sel);
> +		DRM_DEV_ERROR(dsi->dev, "Failed to get GPR regmap: %d\n",
> +			      ret);
> +		return ret;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_ioremap_resource(dsi->dev, res);

You can replace those two calls with devm_platform_ioremap_resource().

> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	dsi->regmap =
> +		devm_regmap_init_mmio(dsi->dev, base, &nwl_dsi_regmap_config);
> +	if (IS_ERR(dsi->regmap)) {
> +		ret = PTR_ERR(dsi->regmap);
> +		DRM_DEV_ERROR(dsi->dev,
> +			      "Failed to create NWL DSI regmap: %d\n", ret);
> +		return ret;
> +	}
> +
> +	dsi->irq = platform_get_irq(pdev, 0);
> +	if (dsi->irq < 0) {
> +		DRM_DEV_ERROR(dsi->dev, "Failed to get device IRQ: %d\n",
> +			      dsi->irq);
> +		return dsi->irq;
> +	}
> +
> +	return 0;
> +}
> +
> +static int imx8mq_dsi_poweron(struct imx_nwl_dsi *dsi)
> +{
> +	/* otherwise the display stays blank */
> +	usleep_range(200, 300);
> +
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, PCLK_RESET_N,
> +			   PCLK_RESET_N);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, ESC_RESET_N,
> +			   ESC_RESET_N);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, RESET_BYTE_N,
> +			   RESET_BYTE_N);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, DPI_RESET_N,
> +			   DPI_RESET_N);
> +
> +	return 0;
> +}
> +
> +static int imx8mq_dsi_poweroff(struct imx_nwl_dsi *dsi)
> +{
> +	if (USE_SRC_RESET_QUIRK(dsi->quirks))
> +		return 0;
> +
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, PCLK_RESET_N, 0);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, ESC_RESET_N, 0);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, RESET_BYTE_N, 0);
> +	regmap_update_bits(dsi->reset, SRC_MIPIPHY_RCR, DPI_RESET_N, 0);
> +	return 0;
> +}
> +
> +static const struct drm_bridge_timings imx_nwl_timings = {
> +	.input_bus_flags = DRM_BUS_FLAG_DE_LOW,
> +};
> +
> +static struct imx_nwl_platform_data imx8mq_dev = {

This structure should be const, especially as it contains function
pointers.

> +	.poweron = &imx8mq_dsi_poweron,
> +	.poweroff = &imx8mq_dsi_poweroff,
> +	.clk_config = {
> +		{ .id = CLK_CORE,   .present = true },
> +		{ .id = CLK_PIXEL,  .present = false },
> +		{ .id = CLK_BYPASS, .present = false },
> +	},
> +	.ext_regs = IMX_REG_SRC | IMX_REG_GPR,
> +};
> +
> +static const struct of_device_id imx_nwl_dsi_dt_ids[] = {
> +	{ .compatible = "fsl,imx8mq-nwl-dsi", .data = &imx8mq_dev, },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, imx_nwl_dsi_dt_ids);
> +
> +static const struct soc_device_attribute imx_nwl_quirks_match[] = {
> +	{ .soc_id = "i.MX8MQ", .revision = "2.0",
> +	  .data = (void *)(E11418_HS_MODE_QUIRK | SRC_RESET_QUIRK) },
> +	{ /* sentinel. */ },
> +};
> +
> +static int imx_nwl_dsi_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	const struct of_device_id *of_id =
> +		of_match_device(imx_nwl_dsi_dt_ids, dev);
> +	const struct imx_nwl_platform_data *pdata = of_id->data;
> +	const struct soc_device_attribute *attr;
> +	struct imx_nwl_dsi *dsi;
> +	int ret;
> +
> +	dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> +	if (!dsi)
> +		return -ENOMEM;
> +
> +	dsi->dev = dev;
> +	dsi->pdata = pdata;
> +	dsi->dpms_mode = DRM_MODE_DPMS_OFF;

DPMS is legacy, let's not use it within the driver.

> +
> +	ret = imx_nwl_dsi_parse_dt(dsi);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_request_irq(dev, dsi->irq, nwl_dsi_irq_handler, 0,
> +			       dev_name(dev), dsi);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to request IRQ: %d (%d)\n", dsi->irq,
> +			      ret);
> +		return ret;
> +	}
> +
> +	dsi->dsi_host.ops = &nwl_dsi_host_ops;
> +	dsi->dsi_host.dev = dev;
> +	ret = mipi_dsi_host_register(&dsi->dsi_host);
> +	if (ret) {
> +		DRM_DEV_ERROR(dev, "Failed to register MIPI host: %d\n", ret);
> +		goto err_cleanup;
> +	}
> +
> +	attr = soc_device_match(imx_nwl_quirks_match);
> +	if (attr)
> +		dsi->quirks = (uintptr_t)attr->data;
> +
> +	dsi->bridge.driver_private = dsi;
> +	dsi->bridge.funcs = &imx_nwl_dsi_bridge_funcs;
> +	dsi->bridge.of_node = dev->of_node;
> +	dsi->bridge.timings = &imx_nwl_timings;
> +
> +	drm_bridge_add(&dsi->bridge);
> +
> +	dev_set_drvdata(dev, dsi);
> +	pm_runtime_enable(dev);
> +	return 0;
> +
> +err_cleanup:
> +	devm_free_irq(dev, dsi->irq, dsi);
> +	return ret;
> +}
> +
> +static int imx_nwl_dsi_remove(struct platform_device *pdev)
> +{
> +	pm_runtime_disable(&pdev->dev);

You should call drm_bridge_remove() here, not in nwl_dsi_host_detach().

> +	return 0;
> +}
> +
> +static struct platform_driver imx_nwl_dsi_driver = {
> +	.probe		= imx_nwl_dsi_probe,
> +	.remove		= imx_nwl_dsi_remove,
> +	.driver		= {
> +		.of_match_table = imx_nwl_dsi_dt_ids,
> +		.name	= DRV_NAME,
> +	},
> +};
> +
> +module_platform_driver(imx_nwl_dsi_driver);
> +
> +MODULE_AUTHOR("NXP Semiconductor");
> +MODULE_AUTHOR("Purism SPC");
> +MODULE_DESCRIPTION("i.MX8 Northwest Logic MIPI-DSI driver");
> +MODULE_LICENSE("GPL"); /* GPLv2 or later */
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.h b/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.h
> new file mode 100644
> index 000000000000..a1e30c58b627
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/nwl-drv.h
> @@ -0,0 +1,72 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * i.MX8 NWL MIPI DSI host driver
> + *
> + * Copyright (C) 2017 NXP
> + * Copyright (C) 2019 Purism SPC
> + */
> +
> +#ifndef __NWL_DRV_H__
> +#define __NWL_DRV_H__
> +
> +#include <drm/drm_mipi_dsi.h>
> +#include <linux/phy/phy.h>
> +
> +struct imx_nwl_platform_data;
> +
> +/* i.MX8 NWL quirks */
> +/* i.MX8MQ errata E11418 */
> +#define E11418_HS_MODE_QUIRK	    BIT(0)
> +#define USE_E11418_HS_MODE_QUIRK(x) ((x) & E11418_HS_MODE_QUIRK)
> +
> +/* Skip DSI bits in SRC on disable to avoid blank display on enable */
> +#define SRC_RESET_QUIRK		    BIT(1)
> +#define USE_SRC_RESET_QUIRK(x)	    ((x) & SRC_RESET_QUIRK)

The USE_* macros are not shorter to type, so I would type out the &
check explicitly.

> +
> +#define NWL_MAX_PLATFORM_CLOCKS 3
> +struct imx_nwl_clk_config {
> +	const char *id;
> +	struct clk *clk;
> +	bool present;
> +	bool enabled;
> +	u32 rate;
> +};
> +
> +struct imx_nwl_dsi {
> +	struct drm_bridge bridge;
> +	struct mipi_dsi_host dsi_host;
> +	struct drm_bridge *panel_bridge;
> +	struct device *dev;
> +	struct phy *phy;
> +	union phy_configure_opts phy_cfg;
> +	unsigned int quirks;
> +
> +	struct regmap *regmap;
> +	int irq;
> +
> +	/* External registers */
> +	struct regmap *csr;
> +	struct regmap *mux_sel;
> +	struct regmap *reset;
> +
> +	/* Platform dependent clocks */
> +	struct imx_nwl_clk_config clk_config[3];

I would use NWL_MAX_PLATFORM_CLOCKS instead of 3 as
imx_nwl_platform_data uses the macro.

> +	/* DSI clocks */
> +	struct clk *phy_ref_clk;
> +	struct clk *rx_esc_clk;
> +	struct clk *tx_esc_clk;
> +
> +	/* dsi lanes */
> +	u32 lanes;
> +	enum mipi_dsi_pixel_format format;
> +	struct videomode vm;
> +	unsigned long dsi_mode_flags;
> +
> +	int dpms_mode;
> +
> +	struct mipi_dsi_transfer *xfer;
> +
> +	const struct imx_nwl_platform_data *pdata;
> +};
> +
> +#endif /* __NWL_DRV_H__ */
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.c b/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.c
> new file mode 100644
> index 000000000000..0e1463af162f
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.c
> @@ -0,0 +1,745 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * NWL DSI host driver
> + *
> + * Copyright (C) 2017 NXP
> + * Copyright (C) 2019 Purism SPC
> + */
> +
> +#include <asm/unaligned.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_crtc_helper.h>
> +#include <drm/drm_of.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_print.h>
> +#include <linux/clk.h>
> +#include <linux/irq.h>
> +#include <linux/regmap.h>
> +#include <video/mipi_display.h>
> +#include <video/videomode.h>
> +
> +#include "nwl-drv.h"
> +#include "nwl-dsi.h"
> +
> +#define MIPI_FIFO_TIMEOUT msecs_to_jiffies(500)
> +
> +/* PKT reg bit manipulation */
> +#define REG_MASK(e, s) (((1 << ((e) - (s) + 1)) - 1) << (s))
> +#define REG_PUT(x, e, s) (((x) << (s)) & REG_MASK(e, s))
> +#define REG_GET(x, e, s) (((x) & REG_MASK(e, s)) >> (s))

Let's not reinvent the wheel, linux/bits.h and linux/bitfield.h can be
used instead.

> +
> +/*
> + * PKT_CONTROL format:
> + * [15: 0] - word count
> + * [17:16] - virtual channel
> + * [23:18] - data type
> + * [24]	   - LP or HS select (0 - LP, 1 - HS)
> + * [25]	   - perform BTA after packet is sent
> + * [26]	   - perform BTA only, no packet tx
> + */
> +#define WC(x)		REG_PUT((x), 15,  0)
> +#define TX_VC(x)	REG_PUT((x), 17, 16)
> +#define TX_DT(x)	REG_PUT((x), 23, 18)
> +#define HS_SEL(x)	REG_PUT((x), 24, 24)
> +#define BTA_TX(x)	REG_PUT((x), 25, 25)
> +#define BTA_NO_TX(x)	REG_PUT((x), 26, 26)
> +
> +/*
> + * RX_PKT_HEADER format:
> + * [15: 0] - word count
> + * [21:16] - data type
> + * [23:22] - virtual channel
> + */
> +#define RX_DT(x) REG_GET((x), 21, 16)
> +#define RX_VC(x) REG_GET((x), 23, 22)
> +
> +/*
> + * DSI Video mode
> + */
> +#define VIDEO_MODE_BURST_MODE_WITH_SYNC_PULSES		0
> +#define VIDEO_MODE_NON_BURST_MODE_WITH_SYNC_EVENTS	BIT(0)
> +#define VIDEO_MODE_BURST_MODE				BIT(1)
> +
> +/*
> + * DPI color coding
> + */
> +#define DPI_16_BIT_565_PACKED	0
> +#define DPI_16_BIT_565_ALIGNED	1
> +#define DPI_16_BIT_565_SHIFTED	2
> +#define DPI_18_BIT_PACKED	3
> +#define DPI_18_BIT_ALIGNED	4
> +#define DPI_24_BIT		5
> +
> +/*
> + * DPI Pixel format
> + */
> +#define PIXEL_FORMAT_16  0
> +#define PIXEL_FORMAT_18  BIT(0)
> +#define PIXEL_FORMAT_18L BIT(1)
> +#define PIXEL_FORMAT_24  (BIT(0) | BIT(1))
> +
> +enum transfer_direction { DSI_PACKET_SEND, DSI_PACKET_RECEIVE };

Line breaks please.

> +
> +struct mipi_dsi_transfer {

Let's not use such a generic name for a driver-specific structure. You
should name is nwl_dsi_transfer.

> +	const struct mipi_dsi_msg *msg;
> +	struct mipi_dsi_packet packet;
> +	struct completion completed;
> +
> +	int status; /* status of transmission */
> +	enum transfer_direction direction;
> +	bool need_bta;
> +	u8 cmd;
> +	u16 rx_word_count;
> +	size_t tx_len; /* bytes sent */
> +	size_t rx_len; /* bytes received */
> +};
> +
> +static inline int nwl_dsi_write(struct imx_nwl_dsi *dsi, unsigned int reg,
> +				u32 val)
> +{
> +	int ret;
> +
> +	ret = regmap_write(dsi->regmap, reg, val);
> +	if (ret < 0)
> +		DRM_DEV_ERROR(dsi->dev,
> +			      "Failed to write NWL DSI reg 0x%x: %d\n", reg,
> +			      ret);
> +	return ret;
> +}
> +
> +static inline u32 nwl_dsi_read(struct imx_nwl_dsi *dsi, u32 reg)
> +{
> +	unsigned int val;
> +	int ret;
> +
> +	ret = regmap_read(dsi->regmap, reg, &val);
> +	if (ret < 0)
> +		DRM_DEV_ERROR(dsi->dev, "Failed to read NWL DSI reg 0x%x: %d\n",
> +			      reg, ret);
> +
> +	return val;

You're loosing the error...

> +}
> +
> +static u32 nwl_dsi_get_dpi_pixel_format(enum mipi_dsi_pixel_format format)
> +{
> +	switch (format) {
> +	case MIPI_DSI_FMT_RGB565:
> +		return PIXEL_FORMAT_16;
> +	case MIPI_DSI_FMT_RGB666:
> +		return PIXEL_FORMAT_18L;
> +	case MIPI_DSI_FMT_RGB666_PACKED:
> +		return PIXEL_FORMAT_18;
> +	case MIPI_DSI_FMT_RGB888:
> +		return PIXEL_FORMAT_24;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +int nwl_dsi_get_dphy_params(struct imx_nwl_dsi *dsi,
> +			    const struct drm_display_mode *mode,
> +			    union phy_configure_opts *phy_opts)
> +{
> +	unsigned long rate;
> +
> +	if (dsi->lanes < 1 || dsi->lanes > 4)
> +		return -EINVAL;
> +
> +	/*
> +	 * So far the DPHY spec minimal timings work for both mixel
> +	 * dphy and nwl dsi host
> +	 */
> +	phy_mipi_dphy_get_default_config(
> +		mode->crtc_clock * 1000,
> +		mipi_dsi_pixel_format_to_bpp(dsi->format), dsi->lanes,
> +		&phy_opts->mipi_dphy);
> +	rate = clk_get_rate(dsi->tx_esc_clk);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "LP clk is @%lu Hz\n", rate);
> +	phy_opts->mipi_dphy.lp_clk_rate = rate;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(nwl_dsi_get_dphy_params);

No need to export symbols, those fubctions are only meant to be called
from within the same module.

> +
> +#define PSEC_PER_SEC 1000000000000LL
> +/*
> + * ps2bc - Picoseconds to byte clock cycles
> + */
> +static u32 ps2bc(struct imx_nwl_dsi *dsi, unsigned long long ps)
> +{
> +	int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +
> +	return DIV_ROUND_UP(ps * dsi->vm.pixelclock * bpp,
> +			    dsi->lanes * 8 * PSEC_PER_SEC);
> +}
> +
> +/**
> + * ui2bc - UI time periods to byte clock cycles
> + */
> +static u32 ui2bc(struct imx_nwl_dsi *dsi, unsigned long long ui)
> +{
> +	int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> +
> +	return DIV_ROUND_UP(ui * dsi->lanes, dsi->vm.pixelclock * bpp);
> +}
> +
> +#define USEC_PER_SEC 1000000L
> +/*
> + * us2bc - micro seconds to lp clock cycles
> + */
> +static u32 us2lp(u32 lp_clk_rate, unsigned long us)
> +{
> +	return DIV_ROUND_UP(us * lp_clk_rate, USEC_PER_SEC);
> +}
> +
> +static int nwl_dsi_config_host(struct imx_nwl_dsi *dsi)
> +{
> +	u32 cycles;
> +	struct phy_configure_opts_mipi_dphy *cfg = &dsi->phy_cfg.mipi_dphy;
> +
> +	if (dsi->lanes < 1 || dsi->lanes > 4)
> +		return -EINVAL;
> +
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "DSI Lanes %d\n", dsi->lanes);
> +	nwl_dsi_write(dsi, CFG_NUM_LANES, dsi->lanes - 1);
> +
> +	if (dsi->dsi_mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS) {
> +		nwl_dsi_write(dsi, CFG_NONCONTINUOUS_CLK, 0x01);
> +		nwl_dsi_write(dsi, CFG_AUTOINSERT_EOTP, 0x01);
> +	} else {
> +		nwl_dsi_write(dsi, CFG_NONCONTINUOUS_CLK, 0x00);
> +		nwl_dsi_write(dsi, CFG_AUTOINSERT_EOTP, 0x00);
> +	}
> +
> +	/* values in byte clock cycles */
> +	cycles = ui2bc(dsi, cfg->clk_pre);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_t_pre: 0x%x\n", cycles);
> +	nwl_dsi_write(dsi, CFG_T_PRE, cycles);
> +	cycles = ps2bc(dsi, cfg->lpx + cfg->clk_prepare + cfg->clk_zero);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_tx_gap (pre): 0x%x\n", cycles);
> +	cycles += ui2bc(dsi, cfg->clk_pre);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_tx_gap: 0x%x\n", cycles);
> +	nwl_dsi_write(dsi, CFG_T_POST, cycles);
> +	cycles = ps2bc(dsi, cfg->hs_exit);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_tx_gap: 0x%x\n", cycles);
> +	nwl_dsi_write(dsi, CFG_TX_GAP, cycles);
> +
> +	nwl_dsi_write(dsi, CFG_EXTRA_CMDS_AFTER_EOTP, 0x01);
> +	nwl_dsi_write(dsi, CFG_HTX_TO_COUNT, 0x00);
> +	nwl_dsi_write(dsi, CFG_LRX_H_TO_COUNT, 0x00);
> +	nwl_dsi_write(dsi, CFG_BTA_H_TO_COUNT, 0x00);
> +	/* In LP clock cycles */
> +	cycles = us2lp(cfg->lp_clk_rate, cfg->wakeup);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "cfg_twakeup: 0x%x\n", cycles);
> +	nwl_dsi_write(dsi, CFG_TWAKEUP, cycles);
> +
> +	return 0;
> +}
> +
> +static int nwl_dsi_config_dpi(struct imx_nwl_dsi *dsi)
> +{
> +	struct videomode *vm = &dsi->vm;
> +	u32 color_format, mode;
> +	bool burst_mode;
> +
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "hfront_porch = %d\n", vm->hfront_porch);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "hback_porch = %d\n", vm->hback_porch);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "hsync_len = %d\n", vm->hsync_len);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "hactive = %d\n", vm->hactive);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "vfront_porch = %d\n", vm->vfront_porch);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "vback_porch = %d\n", vm->vback_porch);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "vsync_len = %d\n", vm->vsync_len);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "vactive = %d\n", vm->vactive);
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "clock = %lu kHz\n",
> +			     vm->pixelclock / 1000);
> +
> +	color_format = nwl_dsi_get_dpi_pixel_format(dsi->format);
> +	if (color_format < 0) {
> +		DRM_DEV_ERROR(dsi->dev, "Invalid color format 0x%x\n",
> +			      dsi->format);
> +		return color_format;
> +	}
> +	DRM_DEV_DEBUG_DRIVER(dsi->dev, "pixel fmt = %d\n", dsi->format);
> +
> +	nwl_dsi_write(dsi, INTERFACE_COLOR_CODING, DPI_24_BIT);
> +	nwl_dsi_write(dsi, PIXEL_FORMAT, color_format);
> +	/*
> +	 * Adjusting input polarity based on the video mode results in
> +	 * a black screen so always pick active low:
> +	 */
> +	nwl_dsi_write(dsi, VSYNC_POLARITY, VSYNC_POLARITY_ACTIVE_LOW);
> +	nwl_dsi_write(dsi, HSYNC_POLARITY, HSYNC_POLARITY_ACTIVE_LOW);
> +
> +	burst_mode = (dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_BURST) &&
> +		     !(dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE);
> +
> +	if (burst_mode) {
> +		nwl_dsi_write(dsi, VIDEO_MODE, VIDEO_MODE_BURST_MODE);
> +		nwl_dsi_write(dsi, PIXEL_FIFO_SEND_LEVEL, 256);
> +	} else {
> +		mode = ((dsi->dsi_mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) ?
> +				VIDEO_MODE_BURST_MODE_WITH_SYNC_PULSES :
> +				VIDEO_MODE_NON_BURST_MODE_WITH_SYNC_EVENTS);
> +		nwl_dsi_write(dsi, VIDEO_MODE, mode);
> +		nwl_dsi_write(dsi, PIXEL_FIFO_SEND_LEVEL, vm->hactive);
> +	}
> +
> +	nwl_dsi_write(dsi, HFP, vm->hfront_porch);
> +	nwl_dsi_write(dsi, HBP, vm->hback_porch);
> +	nwl_dsi_write(dsi, HSA, vm->hsync_len);
> +
> +	nwl_dsi_write(dsi, ENABLE_MULT_PKTS, 0x0);
> +	nwl_dsi_write(dsi, BLLP_MODE, 0x1);
> +	nwl_dsi_write(dsi, ENABLE_MULT_PKTS, 0x0);
> +	nwl_dsi_write(dsi, USE_NULL_PKT_BLLP, 0x0);
> +	nwl_dsi_write(dsi, VC, 0x0);
> +
> +	nwl_dsi_write(dsi, PIXEL_PAYLOAD_SIZE, vm->hactive);
> +	nwl_dsi_write(dsi, VACTIVE, vm->vactive - 1);
> +	nwl_dsi_write(dsi, VBP, vm->vback_porch);
> +	nwl_dsi_write(dsi, VFP, vm->vfront_porch);
> +
> +	return 0;
> +}
> +
> +static int nwl_dsi_enable_tx_clock(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +	int ret;
> +
> +	ret = clk_prepare_enable(dsi->tx_esc_clk);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to enable tx_esc clk: %d\n", ret);
> +		return ret;
> +	}
> +
> +	DRM_DEV_DEBUG_DRIVER(dev, "Enabled tx_esc clk @%lu Hz\n",
> +			     clk_get_rate(dsi->tx_esc_clk));
> +	return 0;
> +}
> +
> +static int nwl_dsi_enable_rx_clock(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +	int ret;
> +
> +	ret = clk_prepare_enable(dsi->rx_esc_clk);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to enable rx_esc clk: %d\n", ret);
> +		return ret;
> +	}
> +
> +	DRM_DEV_DEBUG_DRIVER(dev, "Enabled rx_esc clk @%lu Hz\n",
> +			     clk_get_rate(dsi->rx_esc_clk));
> +	return 0;
> +}
> +
> +static void nwl_dsi_init_interrupts(struct imx_nwl_dsi *dsi)
> +{
> +	u32 irq_enable;
> +
> +	nwl_dsi_write(dsi, IRQ_MASK, 0xffffffff);
> +	nwl_dsi_write(dsi, IRQ_MASK2, 0x7);
> +
> +	irq_enable = ~(u32)(TX_PKT_DONE_MASK | RX_PKT_HDR_RCVD_MASK |
> +			    TX_FIFO_OVFLW_MASK | HS_TX_TIMEOUT_MASK);
> +
> +	nwl_dsi_write(dsi, IRQ_MASK, irq_enable);
> +}
> +
> +static int nwl_dsi_host_attach(struct mipi_dsi_host *dsi_host,
> +			       struct mipi_dsi_device *device)
> +{
> +	struct imx_nwl_dsi *dsi =
> +		container_of(dsi_host, struct imx_nwl_dsi, dsi_host);
> +	struct device *dev = dsi->dev;
> +	struct drm_bridge *bridge;
> +	struct drm_panel *panel;
> +	int ret;
> +
> +	DRM_DEV_INFO(dev, "lanes=%u, format=0x%x flags=0x%lx\n", device->lanes,
> +		     device->format, device->mode_flags);
> +
> +	if (device->lanes < 1 || device->lanes > 4)
> +		return -EINVAL;
> +
> +	dsi->lanes = device->lanes;
> +	dsi->format = device->format;
> +	dsi->dsi_mode_flags = device->mode_flags;
> +
> +	ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 1, 0, &panel,
> +					  &bridge);
> +	if (ret)
> +		return ret;
> +
> +	if (panel) {
> +		bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_DSI);
> +		if (IS_ERR(bridge))
> +			return PTR_ERR(bridge);
> +	}
> +
> +	dsi->panel_bridge = bridge;
> +	drm_bridge_add(&dsi->bridge);
> +
> +	return 0;
> +}
> +
> +static int nwl_dsi_host_detach(struct mipi_dsi_host *dsi_host,
> +			       struct mipi_dsi_device *device)
> +{
> +	struct imx_nwl_dsi *dsi =
> +		container_of(dsi_host, struct imx_nwl_dsi, dsi_host);
> +
> +	drm_of_panel_bridge_remove(dsi->dev->of_node, 1, 0);
> +	drm_bridge_remove(&dsi->bridge);
> +
> +	return 0;
> +}
> +
> +static bool nwl_dsi_read_packet(struct imx_nwl_dsi *dsi, u32 status)
> +{
> +	struct device *dev = dsi->dev;
> +	struct mipi_dsi_transfer *xfer = dsi->xfer;
> +	u8 *payload = xfer->msg->rx_buf;
> +	u32 val;
> +	u16 word_count;
> +	u8 channel;
> +	u8 data_type;
> +
> +	xfer->status = 0;
> +
> +	if (xfer->rx_word_count == 0) {
> +		if (!(status & RX_PKT_HDR_RCVD))
> +			return false;
> +		/* Get the RX header and parse it */
> +		val = nwl_dsi_read(dsi, RX_PKT_HEADER);
> +		word_count = WC(val);
> +		channel = RX_VC(val);
> +		data_type = RX_DT(val);
> +
> +		if (channel != xfer->msg->channel) {
> +			DRM_DEV_ERROR(dev,
> +				      "[%02X] Channel mismatch (%u != %u)\n",
> +				      xfer->cmd, channel, xfer->msg->channel);
> +			return true;
> +		}
> +
> +		switch (data_type) {
> +		case MIPI_DSI_RX_GENERIC_SHORT_READ_RESPONSE_2BYTE:
> +			/* Fall through */
> +		case MIPI_DSI_RX_DCS_SHORT_READ_RESPONSE_2BYTE:
> +			if (xfer->msg->rx_len > 1) {
> +				/* read second byte */
> +				payload[1] = word_count >> 8;
> +				++xfer->rx_len;
> +			}
> +			/* Fall through */
> +		case MIPI_DSI_RX_GENERIC_SHORT_READ_RESPONSE_1BYTE:
> +			/* Fall through */
> +		case MIPI_DSI_RX_DCS_SHORT_READ_RESPONSE_1BYTE:
> +			if (xfer->msg->rx_len > 0) {
> +				/* read first byte */
> +				payload[0] = word_count & 0xff;
> +				++xfer->rx_len;
> +			}
> +			xfer->status = xfer->rx_len;
> +			return true;
> +		case MIPI_DSI_RX_ACKNOWLEDGE_AND_ERROR_REPORT:
> +			word_count &= 0xff;
> +			DRM_DEV_ERROR(dev, "[%02X] DSI error report: 0x%02x\n",
> +				      xfer->cmd, word_count);
> +			xfer->status = -EPROTO;
> +			return true;
> +		}
> +
> +		if (word_count > xfer->msg->rx_len) {
> +			DRM_DEV_ERROR(
> +				dev,
> +				"[%02X] Receive buffer too small: %lu (< %u)\n",
> +				xfer->cmd, xfer->msg->rx_len, word_count);
> +			return true;
> +		}
> +
> +		xfer->rx_word_count = word_count;
> +	} else {
> +		/* Set word_count from previous header read */
> +		word_count = xfer->rx_word_count;
> +	}
> +
> +	/* If RX payload is not yet received, wait for it */
> +	if (!(status & RX_PKT_PAYLOAD_DATA_RCVD))
> +		return false;
> +
> +	/* Read the RX payload */
> +	while (word_count >= 4) {
> +		val = nwl_dsi_read(dsi, RX_PAYLOAD);
> +		payload[0] = (val >> 0) & 0xff;
> +		payload[1] = (val >> 8) & 0xff;
> +		payload[2] = (val >> 16) & 0xff;
> +		payload[3] = (val >> 24) & 0xff;
> +		payload += 4;
> +		xfer->rx_len += 4;
> +		word_count -= 4;
> +	}
> +
> +	if (word_count > 0) {
> +		val = nwl_dsi_read(dsi, RX_PAYLOAD);
> +		switch (word_count) {
> +		case 3:
> +			payload[2] = (val >> 16) & 0xff;
> +			++xfer->rx_len;
> +			/* Fall through */
> +		case 2:
> +			payload[1] = (val >> 8) & 0xff;
> +			++xfer->rx_len;
> +			/* Fall through */
> +		case 1:
> +			payload[0] = (val >> 0) & 0xff;
> +			++xfer->rx_len;
> +			break;
> +		}
> +	}
> +
> +	xfer->status = xfer->rx_len;
> +
> +	return true;
> +}
> +
> +static void nwl_dsi_finish_transmission(struct imx_nwl_dsi *dsi, u32 status)
> +{
> +	struct mipi_dsi_transfer *xfer = dsi->xfer;
> +	bool end_packet = false;
> +
> +	if (!xfer)
> +		return;
> +
> +	if (status & TX_FIFO_OVFLW) {
> +		DRM_DEV_ERROR_RATELIMITED(dsi->dev, "tx fifo overflow\n");
> +		return;
> +	}
> +
> +	if (status & HS_TX_TIMEOUT) {
> +		DRM_DEV_ERROR_RATELIMITED(dsi->dev, "HS tx timeout\n");
> +		return;
> +	}
> +
> +	if (xfer->direction == DSI_PACKET_SEND && status & TX_PKT_DONE) {
> +		xfer->status = xfer->tx_len;
> +		end_packet = true;
> +	} else if (status & DPHY_DIRECTION &&
> +		   ((status & (RX_PKT_HDR_RCVD | RX_PKT_PAYLOAD_DATA_RCVD)))) {
> +		end_packet = nwl_dsi_read_packet(dsi, status);
> +	}
> +
> +	if (end_packet)
> +		complete(&xfer->completed);
> +}
> +
> +static void nwl_dsi_begin_transmission(struct imx_nwl_dsi *dsi)
> +{
> +	struct mipi_dsi_transfer *xfer = dsi->xfer;
> +	struct mipi_dsi_packet *pkt = &xfer->packet;
> +	const u8 *payload;
> +	size_t length;
> +	u16 word_count;
> +	u8 hs_mode;
> +	u32 val;
> +	u32 hs_workaround = 0;
> +
> +	/* Send the payload, if any */
> +	length = pkt->payload_length;
> +	payload = pkt->payload;
> +
> +	while (length >= 4) {
> +		val = get_unaligned_le32(payload);

The framework doesn't guarantee the payload to be aligned on a multiple
of 4 bytes ?

> +		hs_workaround |= !(val & 0xFFFF00);
> +		nwl_dsi_write(dsi, TX_PAYLOAD, val);
> +		payload += 4;
> +		length -= 4;
> +	}
> +	/* Send the rest of the payload */
> +	val = 0;
> +	switch (length) {
> +	case 3:
> +		val |= payload[2] << 16;
> +		/* Fall through */
> +	case 2:
> +		val |= payload[1] << 8;
> +		hs_workaround |= !(val & 0xFFFF00);
> +		/* Fall through */
> +	case 1:
> +		val |= payload[0];
> +		nwl_dsi_write(dsi, TX_PAYLOAD, val);
> +		break;
> +	}
> +	xfer->tx_len = pkt->payload_length;
> +
> +	/*
> +	 * Send the header
> +	 * header[0] = Virtual Channel + Data Type
> +	 * header[1] = Word Count LSB (LP) or first param (SP)
> +	 * header[2] = Word Count MSB (LP) or second param (SP)
> +	 */
> +	word_count = pkt->header[1] | (pkt->header[2] << 8);
> +	if ((hs_workaround && USE_E11418_HS_MODE_QUIRK(dsi->quirks))) {
> +		DRM_DEV_DEBUG_DRIVER(dsi->dev,
> +				     "Using hs mode workaround for cmd 0x%x\n",
> +				     xfer->cmd);
> +		hs_mode = 1;
> +	} else {
> +		hs_mode = (xfer->msg->flags & MIPI_DSI_MSG_USE_LPM) ? 0 : 1;
> +	}
> +	val = WC(word_count) |
> +		TX_VC(xfer->msg->channel) |
> +		TX_DT(xfer->msg->type) |
> +		HS_SEL(hs_mode) |
> +		BTA_TX(xfer->need_bta);
> +	nwl_dsi_write(dsi, PKT_CONTROL, val);
> +
> +	/* Send packet command */
> +	nwl_dsi_write(dsi, SEND_PACKET, 0x1);
> +}
> +
> +static ssize_t nwl_dsi_host_transfer(struct mipi_dsi_host *dsi_host,
> +				     const struct mipi_dsi_msg *msg)
> +{
> +	struct imx_nwl_dsi *dsi =
> +		container_of(dsi_host, struct imx_nwl_dsi, dsi_host);
> +	struct mipi_dsi_transfer xfer;
> +	ssize_t ret = 0;
> +
> +	/* Create packet to be sent */
> +	dsi->xfer = &xfer;
> +	ret = mipi_dsi_create_packet(&xfer.packet, msg);
> +	if (ret < 0) {
> +		dsi->xfer = NULL;
> +		return ret;
> +	}
> +
> +	if ((msg->type & MIPI_DSI_GENERIC_READ_REQUEST_0_PARAM ||
> +	     msg->type & MIPI_DSI_GENERIC_READ_REQUEST_1_PARAM ||
> +	     msg->type & MIPI_DSI_GENERIC_READ_REQUEST_2_PARAM ||
> +	     msg->type & MIPI_DSI_DCS_READ) &&
> +	    msg->rx_len > 0 && msg->rx_buf != NULL)
> +		xfer.direction = DSI_PACKET_RECEIVE;
> +	else
> +		xfer.direction = DSI_PACKET_SEND;
> +
> +	xfer.need_bta = (xfer.direction == DSI_PACKET_RECEIVE);
> +	xfer.need_bta |= (msg->flags & MIPI_DSI_MSG_REQ_ACK) ? 1 : 0;
> +	xfer.msg = msg;
> +	xfer.status = -ETIMEDOUT;
> +	xfer.rx_word_count = 0;
> +	xfer.rx_len = 0;
> +	xfer.cmd = 0x00;
> +	if (msg->tx_len > 0)
> +		xfer.cmd = ((u8 *)(msg->tx_buf))[0];
> +	init_completion(&xfer.completed);
> +
> +	nwl_dsi_enable_rx_clock(dsi);
> +
> +	/* Initiate the DSI packet transmision */
> +	nwl_dsi_begin_transmission(dsi);
> +
> +	if (!wait_for_completion_timeout(&xfer.completed, MIPI_FIFO_TIMEOUT)) {
> +		DRM_DEV_ERROR(dsi_host->dev, "[%02X] DSI transfer timed out\n",
> +			      xfer.cmd);
> +		ret = -ETIMEDOUT;
> +	} else {
> +		ret = xfer.status;
> +	}
> +
> +	clk_disable_unprepare(dsi->rx_esc_clk);
> +
> +	return ret;
> +}
> +
> +const struct mipi_dsi_host_ops nwl_dsi_host_ops = {
> +	.attach = nwl_dsi_host_attach,
> +	.detach = nwl_dsi_host_detach,
> +	.transfer = nwl_dsi_host_transfer,
> +};
> +
> +irqreturn_t nwl_dsi_irq_handler(int irq, void *data)
> +{
> +	u32 irq_status;
> +	struct imx_nwl_dsi *dsi = data;
> +
> +	irq_status = nwl_dsi_read(dsi, IRQ_STATUS);
> +
> +	if (irq_status & TX_PKT_DONE || irq_status & RX_PKT_HDR_RCVD ||
> +	    irq_status & RX_PKT_PAYLOAD_DATA_RCVD)
> +		nwl_dsi_finish_transmission(dsi, irq_status);
> +
> +	return IRQ_HANDLED;
> +}
> +EXPORT_SYMBOL_GPL(nwl_dsi_irq_handler);
> +
> +int nwl_dsi_enable(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +	union phy_configure_opts *phy_cfg = &dsi->phy_cfg;
> +	int ret;
> +
> +	if (!dsi->lanes) {
> +		DRM_DEV_ERROR(dev, "Need DSI lanes: %d\n", dsi->lanes);
> +		return -EINVAL;
> +	}
> +
> +	ret = phy_init(dsi->phy);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to init DSI phy: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = phy_configure(dsi->phy, phy_cfg);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to configure DSI phy: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = nwl_dsi_enable_tx_clock(dsi);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to enable tx clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = nwl_dsi_config_host(dsi);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to set up DSI: %d", ret);
> +		return ret;
> +	}
> +
> +	ret = nwl_dsi_config_dpi(dsi);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to set up DPI: %d", ret);
> +		return ret;
> +	}
> +
> +	ret = phy_power_on(dsi->phy);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "Failed to power on DPHY (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	nwl_dsi_init_interrupts(dsi);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(nwl_dsi_enable);
> +
> +int nwl_dsi_disable(struct imx_nwl_dsi *dsi)
> +{
> +	struct device *dev = dsi->dev;
> +
> +	DRM_DEV_DEBUG_DRIVER(dev, "Disabling clocks and phy\n");
> +
> +	phy_power_off(dsi->phy);
> +	phy_exit(dsi->phy);
> +
> +	/* Disabling the clock before the phy breaks enabling dsi again */
> +	clk_disable_unprepare(dsi->tx_esc_clk);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(nwl_dsi_disable);
> diff --git a/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.h b/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.h
> new file mode 100644
> index 000000000000..7bcf804843e2
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/imx-nwl/nwl-dsi.h
> @@ -0,0 +1,111 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * i.MX8 NWL MIPI DSI host driver
> + *
> + * Copyright (C) 2017 NXP
> + * Copyright (C) 2019 Purism SPC
> + */
> +#ifndef __NWL_DSI_H__
> +#define __NWL_DSI_H__
> +
> +#include <drm/drm_mipi_dsi.h>
> +
> +/* DSI HOST registers */
> +#define CFG_NUM_LANES			0x0

Some of the register names are quite prone to namespace clashes. I
recommend prefixing them all with NWL_DSI_.

> +#define CFG_NONCONTINUOUS_CLK		0x4
> +#define CFG_T_PRE			0x8
> +#define CFG_T_POST			0xc
> +#define CFG_TX_GAP			0x10
> +#define CFG_AUTOINSERT_EOTP		0x14
> +#define CFG_EXTRA_CMDS_AFTER_EOTP	0x18
> +#define CFG_HTX_TO_COUNT		0x1c
> +#define CFG_LRX_H_TO_COUNT		0x20
> +#define CFG_BTA_H_TO_COUNT		0x24
> +#define CFG_TWAKEUP			0x28
> +#define CFG_STATUS_OUT			0x2c
> +#define RX_ERROR_STATUS			0x30
> +
> +/* DSI DPI registers */
> +#define PIXEL_PAYLOAD_SIZE		0x200
> +#define PIXEL_FIFO_SEND_LEVEL		0x204
> +#define INTERFACE_COLOR_CODING		0x208
> +#define PIXEL_FORMAT			0x20c
> +#define VSYNC_POLARITY			0x210
> +#define VSYNC_POLARITY_ACTIVE_LOW	0
> +#define VSYNC_POLARITY_ACTIVE_HIGH	BIT(1)
> +
> +#define HSYNC_POLARITY			0x214
> +#define HSYNC_POLARITY_ACTIVE_LOW	0
> +#define HSYNC_POLARITY_ACTIVE_HIGH	BIT(1)
> +
> +#define VIDEO_MODE			0x218
> +#define HFP				0x21c
> +#define HBP				0x220
> +#define HSA				0x224
> +#define ENABLE_MULT_PKTS		0x228
> +#define VBP				0x22c
> +#define VFP				0x230
> +#define BLLP_MODE			0x234
> +#define USE_NULL_PKT_BLLP		0x238
> +#define VACTIVE				0x23c
> +#define VC				0x240
> +
> +/* DSI APB PKT control */
> +#define TX_PAYLOAD			0x280
> +#define PKT_CONTROL			0x284
> +#define SEND_PACKET			0x288
> +#define PKT_STATUS			0x28c
> +#define PKT_FIFO_WR_LEVEL		0x290
> +#define PKT_FIFO_RD_LEVEL		0x294
> +#define RX_PAYLOAD			0x298
> +#define RX_PKT_HEADER			0x29c
> +
> +/* DSI IRQ handling */
> +#define IRQ_STATUS			0x2a0
> +#define SM_NOT_IDLE			BIT(0)
> +#define TX_PKT_DONE			BIT(1)
> +#define DPHY_DIRECTION			BIT(2)
> +#define TX_FIFO_OVFLW			BIT(3)
> +#define TX_FIFO_UDFLW			BIT(4)
> +#define RX_FIFO_OVFLW			BIT(5)
> +#define RX_FIFO_UDFLW			BIT(6)
> +#define RX_PKT_HDR_RCVD			BIT(7)
> +#define RX_PKT_PAYLOAD_DATA_RCVD	BIT(8)
> +#define BTA_TIMEOUT			BIT(29)
> +#define LP_RX_TIMEOUT			BIT(30)
> +#define HS_TX_TIMEOUT			BIT(31)
> +
> +#define IRQ_STATUS2			0x2a4
> +#define SINGLE_BIT_ECC_ERR		BIT(0)
> +#define MULTI_BIT_ECC_ERR		BIT(1)
> +#define CRC_ERR				BIT(2)
> +
> +#define IRQ_MASK			0x2a8
> +#define SM_NOT_IDLE_MASK		BIT(0)
> +#define TX_PKT_DONE_MASK		BIT(1)
> +#define DPHY_DIRECTION_MASK		BIT(2)
> +#define TX_FIFO_OVFLW_MASK		BIT(3)
> +#define TX_FIFO_UDFLW_MASK		BIT(4)
> +#define RX_FIFO_OVFLW_MASK		BIT(5)
> +#define RX_FIFO_UDFLW_MASK		BIT(6)
> +#define RX_PKT_HDR_RCVD_MASK		BIT(7)
> +#define RX_PKT_PAYLOAD_DATA_RCVD_MASK	BIT(8)
> +#define BTA_TIMEOUT_MASK		BIT(29)
> +#define LP_RX_TIMEOUT_MASK		BIT(30)
> +#define HS_TX_TIMEOUT_MASK		BIT(31)
> +
> +#define IRQ_MASK2			0x2ac
> +#define SINGLE_BIT_ECC_ERR_MASK		BIT(0)
> +#define MULTI_BIT_ECC_ERR_MASK		BIT(1)
> +#define CRC_ERR_MASK			BIT(2)
> +
> +extern const struct mipi_dsi_host_ops nwl_dsi_host_ops;
> +
> +irqreturn_t nwl_dsi_irq_handler(int irq, void *data);
> +int nwl_dsi_enable(struct imx_nwl_dsi *dsi);
> +int nwl_dsi_disable(struct imx_nwl_dsi *dsi);
> +int nwl_dsi_get_dphy_params(struct imx_nwl_dsi *dsi,
> +			    const struct drm_display_mode *mode,
> +			    union phy_configure_opts *phy_opts);
> +
> +#endif /* __NWL_DSI_H__ */

-- 
Regards,

Laurent Pinchart

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