linux-kernel - Re: [PATCH 3/3] drm/panel: visionox-rm69299: Add backlight support

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Message-ID: <b49e2a94-695e-42ec-99de-aed42e62572d@linaro.org>
Date: Tue, 2 Sep 2025 09:34:09 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Guido Günther <agx@...xcpu.org>,
 Jessica Zhang <jessica.zhang@....qualcomm.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 phone-devel@...r.kernel.org
Subject: Re: [PATCH 3/3] drm/panel: visionox-rm69299: Add backlight support

On 01/09/2025 16:22, Guido Günther wrote:
> The shift6mq's variant supports controlling the backlight via DSI
> commands. Use that if a max_brightness is set in the device specific
> data.
> 
> Signed-off-by: Guido Günther <agx@...xcpu.org>
> ---
>   drivers/gpu/drm/panel/panel-visionox-rm69299.c | 67 ++++++++++++++++++++++++++
>   1 file changed, 67 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-visionox-rm69299.c b/drivers/gpu/drm/panel/panel-visionox-rm69299.c
> index 2216d38366ea37368d15480f9d8a8ccbfe77ba3b..5e5ff6056c80e67a5bf8fe4911cdbc588db5d03b 100644
> --- a/drivers/gpu/drm/panel/panel-visionox-rm69299.c
> +++ b/drivers/gpu/drm/panel/panel-visionox-rm69299.c
> @@ -3,6 +3,7 @@
>    * Copyright (c) 2019, The Linux Foundation. All rights reserved.
>    */
>   
> +#include <linux/backlight.h>
>   #include <linux/delay.h>
>   #include <linux/module.h>
>   #include <linux/property.h>
> @@ -20,6 +21,8 @@ struct visionox_rm69299_panel_desc {
>   	const struct drm_display_mode *mode;
>   	const u8 *init_seq;
>   	unsigned int init_seq_len;
> +	int max_brightness;
> +	int initial_brightness;
>   };
>   
>   struct visionox_rm69299 {
> @@ -285,6 +288,63 @@ static const struct drm_panel_funcs visionox_rm69299_drm_funcs = {
>   	.get_modes = visionox_rm69299_get_modes,
>   };
>   
> +static int visionox_rm69299_bl_get_brightness(struct backlight_device *bl)
> +{
> +	struct mipi_dsi_device *dsi = bl_get_data(bl);
> +	u16 brightness;
> +	int ret;
> +
> +	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
> +
> +	ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness);
> +	if (ret < 0)
> +		return ret;
> +
> +	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> +	return brightness;
> +}
> +
> +static int visionox_rm69299_bl_update_status(struct backlight_device *bl)
> +{
> +	struct mipi_dsi_device *dsi = bl_get_data(bl);
> +	u16 brightness = backlight_get_brightness(bl);
> +	int ret;
> +
> +	dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
> +
> +	ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
> +	if (ret < 0)
> +		return ret;
> +
> +	dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> +	return 0;
> +}
> +
> +static const struct backlight_ops visionox_rm69299_bl_ops = {
> +	.update_status = visionox_rm69299_bl_update_status,
> +	.get_brightness = visionox_rm69299_bl_get_brightness,
> +};
> +
> +static struct backlight_device *
> +visionox_rm69299_create_backlight(struct visionox_rm69299 *ctx)
> +{
> +	struct device *dev = &ctx->dsi->dev;
> +	const struct backlight_properties props = {
> +		.type = BACKLIGHT_RAW,
> +		.brightness = ctx->desc->initial_brightness,
> +		.max_brightness = ctx->desc->max_brightness,
> +	};
> +
> +	if (!ctx->desc->max_brightness)
> +		return 0;
> +
> +	return devm_backlight_device_register(dev, dev_name(dev), dev, ctx->dsi,
> +					      &visionox_rm69299_bl_ops,
> +					      &props);
> +}
> +
>   static int visionox_rm69299_probe(struct mipi_dsi_device *dsi)
>   {
>   	struct device *dev = &dsi->dev;
> @@ -316,6 +376,11 @@ static int visionox_rm69299_probe(struct mipi_dsi_device *dsi)
>   		return PTR_ERR(ctx->reset_gpio);
>   	}
>   
> +	ctx->panel.backlight = visionox_rm69299_create_backlight(ctx);
> +	if (IS_ERR(ctx->panel.backlight))
> +		return dev_err_probe(dev, PTR_ERR(ctx->panel.backlight),
> +				     "Failed to create backlight\n");
> +
>   	drm_panel_add(&ctx->panel);
>   
>   	dsi->lanes = 4;
> @@ -353,6 +418,8 @@ const struct visionox_rm69299_panel_desc visionox_rm69299_shift_desc = {
>   	.mode = &visionox_rm69299_1080x2160_60hz,
>   	.init_seq = (const u8 *)visionox_rm69299_1080x2160_60hz_init_seq,
>   	.init_seq_len = ARRAY_SIZE(visionox_rm69299_1080x2160_60hz_init_seq),
> +	.max_brightness = 255,
> +	.initial_brightness = 50,
>   };
>   
>   static const struct of_device_id visionox_rm69299_of_match[] = {
> 

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>