Subject: Re: [PATCH v9 2/2] drm/bridge: Add NWL MIPI DSI host controller support

From: Sam Ravnborg <[email-masked]>
Date: Wed, 18 Mar 2020 22:46:39 +0100

Hi Guido.

Impressive and very detailed changelog in intro mail - nice.

On Wed, Mar 18, 2020 at 04:09:08PM +0100, 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]>
> Signed-off-by: Robert Chiras <[email-masked]>
> Tested-by: Robert Chiras <[email-masked]>
> Tested-by: Martin Kepplinger <[email-masked]>
> ---
>  drivers/gpu/drm/bridge/Kconfig   |   16 +
>  drivers/gpu/drm/bridge/Makefile  |    3 +
>  drivers/gpu/drm/bridge/nwl-dsi.c | 1213 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/bridge/nwl-dsi.h |  144 ++++
>  4 files changed, 1376 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/nwl-dsi.c
>  create mode 100644 drivers/gpu/drm/bridge/nwl-dsi.h
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 8397bf72d2f3..d41d93d24f16 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -55,6 +55,22 @@ config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
>  	  to DP++. This is used with the i.MX6 imx-ldb
>  	  driver. You are likely to say N here.
>  
> +config DRM_NWL_MIPI_DSI
> +	tristate "Northwest Logic MIPI DSI Host controller"
> +	depends on DRM
> +	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 MULTIPLEXER
> +	select REGMAP_MMIO
> +	help
> +	  This enables the Northwest Logic MIPI DSI Host controller as
> +	  for example found on NXP's i.MX8 Processors.
> +
>  config DRM_NXP_PTN3460
>  	tristate "NXP PTN3460 DP/LVDS bridge"
>  	depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 1eb5376c5d68..98581b3128a3 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -15,6 +15,9 @@ obj-$(CONFIG_DRM_TOSHIBA_TC358767) += tc358767.o
>  obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
>  obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
>  obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
> +obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
>  
>  obj-y += analogix/
>  obj-y += synopsys/
> +
> +header-test-y += nwl-dsi.h
Sorry - but header-test-y support was ripped out of the kernel again.
So this line has no longer any effect.

> +
> +static void nwl_dsi_bridge_enable(struct drm_bridge *bridge)
> +{
> +	struct nwl_dsi *dsi = bridge_to_dsi(bridge);
> +	int ret;
> +
> +	/* Step 5 from DSI reset-out instructions */
> +	ret = reset_control_deassert(dsi->rst_dpi);
> +	if (ret < 0)
> +		DRM_DEV_ERROR(dsi->dev, "Failed to deassert DPI: %d\n", ret);
I picked this for a general comment.

    We have drm_err(drm, "...", ...) which is preferred over DRM_XXX
    They require a drm_device * that may not be available everywhere.

IMO not a showstopper, but should be trivial to fix (if adrm_device * is
a avaiable).

> +}
> +
> +static int nwl_dsi_bridge_attach(struct drm_bridge *bridge)
> +{
> +	struct nwl_dsi *dsi = bridge_to_dsi(bridge);
> +	struct drm_bridge *panel_bridge;
> +	struct drm_panel *panel;
> +	int ret;

This function now takes a flags argument.
In other words - the driver will not build when applied
to drm-misc-next.

> +
> +	ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 1, 0, &panel,
> +					  &panel_bridge);
> +	if (ret)
> +		return ret;
> +
> +	if (panel) {
> +		panel_bridge = drm_panel_bridge_add(panel);
> +		if (IS_ERR(panel_bridge))
> +			return PTR_ERR(panel_bridge);
> +	}
> +	dsi->panel_bridge = panel_bridge;
> +
> +	if (!dsi->panel_bridge)
> +		return -EPROBE_DEFER;
> +
> +	return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge);
> +}

	Sam

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