linux-kernel - Re: [PATCH v2 2/2] drm/panel: Add support for Raydium RM67191 panel driver

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Date:   Wed, 19 Jun 2019 15:25:46 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Robert Chiras <robert.chiras@....com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH v2 2/2] drm/panel: Add support for Raydium RM67191 panel
 driver

On Tue, Jun 18, 2019 at 04:30:46PM +0300, Robert Chiras wrote:
> This patch adds Raydium RM67191 TFT LCD panel driver (MIPI-DSI
> protocol).
> 
> Signed-off-by: Robert Chiras <robert.chiras@....com>
Please include in the changelog a list of what was updated - like this:

v2:
- added kconif symbol sorted (sam)
- another nitpick (foo)
- etc

In general try to namme who gave feedback to give them some credit.

Who is maintainer for this onwards?

> ---
>  drivers/gpu/drm/panel/Kconfig                 |   9 +
>  drivers/gpu/drm/panel/Makefile                |   1 +
>  drivers/gpu/drm/panel/panel-raydium-rm67191.c | 709 ++++++++++++++++++++++++++
>  3 files changed, 719 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-raydium-rm67191.c
> 
> +static int rad_panel_prepare(struct drm_panel *panel)
> +{
> +	struct rad_panel *rad = to_rad_panel(panel);
> +
> +	if (rad->prepared)
> +		return 0;
> +
> +	if (rad->reset) {
> +		gpiod_set_value_cansleep(rad->reset, 1);
> +		usleep_range(3000, 5000);
> +		gpiod_set_value_cansleep(rad->reset, 0);

So writing a 0 will release reset.
> +		usleep_range(18000, 20000);
> +	}
> +
> +	rad->prepared = true;
> +
> +	return 0;
> +}
> +
> +static int rad_panel_unprepare(struct drm_panel *panel)
> +{
> +	struct rad_panel *rad = to_rad_panel(panel);
> +
> +	if (!rad->prepared)
> +		return 0;
> +
> +	if (rad->reset) {
> +		gpiod_set_value_cansleep(rad->reset, 1);
> +		usleep_range(15000, 17000);
> +		gpiod_set_value_cansleep(rad->reset, 0);
Looks strange that reset is released in unprepare.
I would expect it to stay reset to minimize power etc.

> +
> +	ret = drm_display_info_set_bus_formats(&connector->display_info,
> +					       rad_bus_formats,
> +					       ARRAY_SIZE(rad_bus_formats));

Other drivers has this as the last stement in their enable function.
I did not check why, but maybe something to invest a few minutes into.
Be different only if there is a reason to do so.

> +	if (ret)
> +		return ret;
> +
> +	drm_mode_probed_add(panel->connector, mode);
> +
> +	return 1;
> +}
> +
> +
> +#ifdef CONFIG_PM
> +static int rad_panel_suspend(struct device *dev)
> +{
> +	struct rad_panel *rad = dev_get_drvdata(dev);
> +
> +	if (!rad->reset)
> +		return 0;
> +
> +	devm_gpiod_put(dev, rad->reset);
> +	rad->reset = NULL;
> +
> +	return 0;
> +}
> +
> +static int rad_panel_resume(struct device *dev)
> +{
> +	struct rad_panel *rad = dev_get_drvdata(dev);
> +
> +	if (rad->reset)
> +		return 0;
> +
> +	rad->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(rad->reset))
> +		rad->reset = NULL;
> +
> +	return PTR_ERR_OR_ZERO(rad->reset);
> +}
> +
> +#endif

Use __maybe_unused for the tw functions above.
And loose the ifdef...

> +
> +static const struct dev_pm_ops rad_pm_ops = {
> +	SET_RUNTIME_PM_OPS(rad_panel_suspend, rad_panel_resume, NULL)
> +	SET_SYSTEM_SLEEP_PM_OPS(rad_panel_suspend, rad_panel_resume)
> +};
> +
> +static const struct of_device_id rad_of_match[] = {
> +	{ .compatible = "raydium,rm67191", },
> +	{ }
We often, but not always, write this as { /* sentinal */ },

> +};
> +MODULE_DEVICE_TABLE(of, rad_of_match);
> +
> +static struct mipi_dsi_driver rad_panel_driver = {
> +	.driver = {
> +		.name = "panel-raydium-rm67191",
> +		.of_match_table = rad_of_match,
> +		.pm	= &rad_pm_ops,
> +	},
> +	.probe = rad_panel_probe,
> +	.remove = rad_panel_remove,
> +	.shutdown = rad_panel_shutdown,
> +};
> +module_mipi_dsi_driver(rad_panel_driver);
> +
> +MODULE_AUTHOR("Robert Chiras <robert.chiras@....com>");
> +MODULE_DESCRIPTION("DRM Driver for Raydium RM67191 MIPI DSI panel");
> +MODULE_LICENSE("GPL v2");

With the above trivialities considered/fixed:
Reviewed-by: Sam Ravnborg <sam@...nborg.org>

	Sam