Re: [PATCH 3/3] drm/panel: himax-hx83121a: add backlight regulator support

[Neil Armstrong <neil.armstrong@linaro.org>]

On 6/8/26 18:26, Icenowy Zheng wrote:
> The backlight, when managed by the panel controller, could be powered by
> an external regulator, and shutting down the regulator could power off
> the backlight.
> 
> Add support for such a regulator. It's powered off when the backlight is
> 0 (either by setting brightness to 0 or setting bl_power), and powered
> on when the backlight should be operating.
> 
> Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
> ---
>   drivers/gpu/drm/panel/panel-himax-hx83121a.c | 26 ++++++++++++++++++++
>   1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-himax-hx83121a.c b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> index 1a7e0125bced8..e31e2fba0a787 100644
> --- a/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> +++ b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
> @@ -34,7 +34,9 @@ struct himax {
>   	struct drm_dsc_config dsc;
>   	struct gpio_desc *reset_gpio;
>   	struct regulator_bulk_data *supplies;
> +	struct regulator *bl_supply;
>   	struct backlight_device *backlight;
> +	bool backlight_enabled;
>   };
>   
>   struct panel_desc {
> @@ -195,7 +197,27 @@ static int himax_bl_update_status(struct backlight_device *bl)
>   {
>   	struct himax *ctx = bl_get_data(bl);
>   	u16 brightness = backlight_get_brightness(bl);
> +	int ret = 0;
> +
> +	if (!brightness) {
> +		if (ctx->backlight_enabled)
> +			ret = regulator_disable(ctx->bl_supply);
> +		if (ret)
> +			return ret;
> +
> +		ctx->backlight_enabled = false;
> +
> +		return 0;
> +	}
> +
>   	/* TODO: brightness to raw map table */
> +	if (!ctx->backlight_enabled)
> +		ret = regulator_enable(ctx->bl_supply);
> +	if (ret)
> +		return ret;
> +
> +	ctx->backlight_enabled = true;
> +
>   	return mipi_dsi_dcs_set_display_brightness_large(to_primary_dsi(ctx),
>   							 brightness);
>   }
> @@ -647,6 +669,10 @@ static int himax_probe(struct mipi_dsi_device *dsi)
>   	ctx->panel.prepare_prev_first = true;
>   
>   	if (desc->has_dcs_backlight) {
> +		ctx->bl_supply = devm_regulator_get_optional(dev, "bl");
> +		if (IS_ERR(ctx->bl_supply))
> +			return dev_err_probe(dev, PTR_ERR(ctx->bl_supply),
> +					     "Failed to get backlight supply\n");
>   		ctx->backlight = himax_create_backlight(ctx);
>   		if (IS_ERR(ctx->backlight))
>   			return dev_err_probe(dev, PTR_ERR(ctx->backlight),

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

Thanks,
Neil