Subject: Re: [PATCH 4/4] drm/panel: Add Rondo RB070D30 panel

From: Sam Ravnborg <[email-masked]>
Date: Sat, 26 Jan 2019 16:39:46 +0100

Hi Maxime / Konstantin.

Nice welstructured and small driver.
Please see a few comments below

Some of the comments in the following apply to a lot of
the existing panel drivers as well.
But lets see if we can get new drivers to be even better.

	Sam 

On Wed, Jan 23, 2019 at 04:54:24PM +0100, Maxime Ripard wrote:
> From: Konstantin Sudakov <[email-masked]>
> 
> The Rondo RB070D30 panel is a MIPI-DSI panel based on a Fitipower EK79007
> controller and a 1024x600 panel.
> 
> Signed-off-by: Konstantin Sudakov <[email-masked]>
> Signed-off-by: Maxime Ripard <[email-masked]>
> ---
>  drivers/gpu/drm/panel/Kconfig                |   9 +-
>  drivers/gpu/drm/panel/Makefile               |   1 +-
>  drivers/gpu/drm/panel/panel-rondo-rb070d30.c | 258 ++++++++++++++++++++-
>  3 files changed, 268 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-rondo-rb070d30.c
> 
> diff --git a/drivers/gpu/drm/panel/panel-rondo-rb070d30.c b/drivers/gpu/drm/panel/panel-rondo-rb070d30.c
> new file mode 100644
> index 000000000000..4f8e63f367b1
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-rondo-rb070d30.c
> @@ -0,0 +1,258 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2018, Bridge Systems BV
> + * Copyright (C) 2018, Bootlin
> + * Copyright (C) 2017, Free Electrons
> + *
> + * This file based on panel-ilitek-ili9881c.c
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/fb.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drmP.h>
> +#include <drm/drm_panel.h>
Please do not use drmP.h in new drivers. We are trying to get rid of it.

> +
> +#include <video/mipi_display.h>
> +#include <video/of_display_timing.h>
> +#include <video/videomode.h>
> +
> +struct rb070d30_panel {
> +	struct drm_panel panel;
> +	struct mipi_dsi_device *dsi;
> +	struct backlight_device *backlight;
> +	struct regulator *supply;
> +
> +	struct {
> +		struct gpio_desc *power;
> +		struct gpio_desc *reset;
> +		struct gpio_desc *updn;
> +		struct gpio_desc *shlr;
> +	} gpios;
> +};
> +
> +static inline struct rb070d30_panel *panel_to_rb070d30_panel(struct drm_panel *panel)
> +{
> +	return container_of(panel, struct rb070d30_panel, panel);
> +}
> +
> +static int rb070d30_panel_prepare(struct drm_panel *panel)
> +{
> +	struct rb070d30_panel *ctx = panel_to_rb070d30_panel(panel);
> +	int ret;
> +
> +	ret = regulator_enable(ctx->supply);
> +	if (ret < 0) {
> +		dev_err(&ctx->dsi->dev, "Failed to enable supply: %d\n", ret);
Use DRM_DEV_ERROR(...) to have consistent error message for the drm drivers.
This is general for the whole file.

> +		return ret;
> +	}
> +
> +	/* Reset */
> +	msleep(20);
> +	gpiod_set_value(ctx->gpios.power, 1);
> +	msleep(20);
> +	gpiod_set_value(ctx->gpios.reset, 1);
> +	msleep(20);
> +	return 0;
> +}
To verify the above pointer to a datasheet would be nice.

> +
> +static int rb070d30_panel_unprepare(struct drm_panel *panel)
> +{
> +	struct rb070d30_panel *ctx = panel_to_rb070d30_panel(panel);
> +
> +	gpiod_set_value(ctx->gpios.power, 0);
> +	gpiod_set_value(ctx->gpios.reset, 0);
> +	regulator_disable(ctx->supply);
> +
> +	return 0;
> +}
There is sometimes timing constrains after deassert reset..
The order is not strictly reverse of prepare - is that on purpose?

> +
> +static int rb070d30_panel_enable(struct drm_panel *panel)
> +{
> +	struct rb070d30_panel *ctx = panel_to_rb070d30_panel(panel);
> +	int ret;
> +
> +	ret = mipi_dsi_dcs_exit_sleep_mode(ctx->dsi);
> +	if (ret)
> +		return ret;
> +
> +	ret = backlight_enable(ctx->backlight);
> +	if (ret)
> +		goto out;
> +
> +	return 0;
> +
> +out:
> +	mipi_dsi_dcs_enter_sleep_mode(ctx->dsi);
> +	return ret;
> +}
> +
> +static int rb070d30_panel_disable(struct drm_panel *panel)
> +{
> +	struct rb070d30_panel *ctx = panel_to_rb070d30_panel(panel);
> +
> +	backlight_disable(ctx->backlight);
> +	return mipi_dsi_dcs_enter_sleep_mode(ctx->dsi);
> +}
> +
> +/* Default timings */
> +static const struct drm_display_mode default_mode = {
> +	.clock		= 51206,
> +	.hdisplay	= 1024,
> +	.hsync_start	= 1024 + 160,
> +	.hsync_end	= 1024 + 160 + 80,
> +	.htotal		= 1024 + 160 + 80 + 80,
> +	.vdisplay	= 600,
> +	.vsync_start	= 600 + 12,
> +	.vsync_end	= 600 + 12 + 10,
> +	.vtotal		= 600 + 12 + 10 + 13,
> +	.vrefresh	= 60,
> +};
height and width missing here. Seems better to add them here than hiding in code below.
Is it on purpose that no flags are specified?

> +
> +static int rb070d30_panel_get_modes(struct drm_panel *panel)
> +{
> +	struct drm_connector *connector = panel->connector;
> +	struct rb070d30_panel *ctx = panel_to_rb070d30_panel(panel);
> +	struct drm_display_mode *mode;
> +	static const u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> +
> +	mode = drm_mode_duplicate(panel->drm, &default_mode);
> +	if (!mode) {
> +		dev_err(&ctx->dsi->dev, "failed to add mode %ux%ux@%u\n",
> +			default_mode.hdisplay, default_mode.vdisplay,
> +			default_mode.vrefresh);
Use"
		DRM_DEV_ERROR(&ctx->dsi->dev,
			      "failed to add mode" DRM_MODE_FMT,
			      DRM_MODE_ARG(mode));
> +		return -EINVAL;
> +	}
> +
> +	drm_mode_set_name(mode);
> +
> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +	drm_mode_probed_add(connector, mode);
> +
> +	panel->connector->display_info.bpc = 8;
> +	panel->connector->display_info.width_mm = 154;
> +	panel->connector->display_info.height_mm = 85;
See comment on height above.
Same goes for bpc

> +	drm_display_info_set_bus_formats(&connector->display_info,
> +					 &bus_format, 1);
> +
> +	return 1;
> +}
> +
> +static const struct drm_panel_funcs rb070d30_panel_funcs = {
> +	.get_modes	= rb070d30_panel_get_modes,
> +	.prepare	= rb070d30_panel_prepare,
> +	.enable		= rb070d30_panel_enable,
> +	.disable	= rb070d30_panel_disable,
> +	.unprepare	= rb070d30_panel_unprepare,
> +};
> +
> +static int rb070d30_panel_dsi_probe(struct mipi_dsi_device *dsi)
> +{
> +	struct device_node *np;
> +	struct rb070d30_panel *ctx;
> +	int ret;
> +
> +	ctx = devm_kzalloc(&dsi->dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	ctx->supply = devm_regulator_get(&dsi->dev, "vcc-lcd");
> +	if (IS_ERR(ctx->supply))
> +		return PTR_ERR(ctx->supply);
> +
> +	mipi_dsi_set_drvdata(dsi, ctx);
> +	ctx->dsi = dsi;
> +
> +	drm_panel_init(&ctx->panel);
> +	ctx->panel.dev = &dsi->dev;
> +	ctx->panel.funcs = &rb070d30_panel_funcs;
> +
> +	ctx->gpios.reset = devm_gpiod_get(&dsi->dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(ctx->gpios.reset)) {
> +		dev_err(&dsi->dev, "Couldn't get our reset GPIO\n");
> +		return PTR_ERR(ctx->gpios.reset);
> +	}
> +
> +	ctx->gpios.power = devm_gpiod_get(&dsi->dev, "power", GPIOD_OUT_LOW);
> +	if (IS_ERR(ctx->gpios.power)) {
> +		dev_err(&dsi->dev, "Couldn't get our power GPIO\n");
> +		return PTR_ERR(ctx->gpios.power);
> +	}
> +
> +	ctx->gpios.updn = devm_gpiod_get(&dsi->dev, "updn", GPIOD_OUT_LOW);
> +	if (IS_ERR(ctx->gpios.updn)) {
> +		dev_err(&dsi->dev, "Couldn't get our updn GPIO\n");
> +		return PTR_ERR(ctx->gpios.updn);
> +	}
This gpio is never used, it is only read from DT

> +
> +	ctx->gpios.shlr = devm_gpiod_get(&dsi->dev, "shlr", GPIOD_OUT_LOW);
> +	if (IS_ERR(ctx->gpios.shlr)) {
> +		dev_err(&dsi->dev, "Couldn't get our shlr GPIO\n");
> +		return PTR_ERR(ctx->gpios.shlr);
> +	}
This gpio is never used, it is only read from DT

> +
> +	np = of_parse_phandle(dsi->dev.of_node, "backlight", 0);
> +	if (np) {
> +		ctx->backlight = of_find_backlight_by_node(np);
> +		of_node_put(np);
> +
> +		if (!ctx->backlight)
> +			return -EPROBE_DEFER;
> +	}
Use devm_of_find_backlight()

> +
> +	ret = drm_panel_add(&ctx->panel);
> +	if (ret < 0)
> +		goto free_backlight;
> +
> +	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_LPM;
> +	dsi->format = MIPI_DSI_FMT_RGB888;
> +	dsi->lanes = 4;
> +
> +	return mipi_dsi_attach(dsi);
> +
> +free_backlight:
> +	backlight_put(ctx->backlight);
If devm_of_find_backlight() is used this can go.

> +	return ret;
> +}
> +
> +static int rb070d30_panel_dsi_remove(struct mipi_dsi_device *dsi)
> +{
> +	struct rb070d30_panel *ctx = mipi_dsi_get_drvdata(dsi);
> +
> +	mipi_dsi_detach(dsi);
> +	drm_panel_remove(&ctx->panel);
> +	backlight_put(ctx->backlight);
If devm_of_find_backlight() is used this can go.

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id rb070d30_panel_of_match[] = {
> +	{ .compatible = "rondo,rb070d30" },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, rb070d30_panel_of_match);
> +
> +static struct mipi_dsi_driver rb070d30_panel_driver = {
> +	.probe = rb070d30_panel_dsi_probe,
> +	.remove = rb070d30_panel_dsi_remove,
> +	.driver = {
> +		.name = "panel-rondo-rb070d30",
> +		.of_match_table	= rb070d30_panel_of_match,
> +	},
> +};
> +module_mipi_dsi_driver(rb070d30_panel_driver);
> +
> +MODULE_AUTHOR("Boris Brezillon <[email-masked]>");
> +MODULE_AUTHOR("Konstantin Sudakov <[email-masked]>");
> +MODULE_DESCRIPTION("Rondo RB070D30 Panel Driver");
> +MODULE_LICENSE("GPL");
> -- 
> git-series 0.9.1
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