linux-kernel - Re: [PATCH 3/5] drm/panel: nt36523: Add DCS backlight support

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Message-ID: <ZDdhu3OprlFNyUO4@Gentoo>
Date:   Thu, 13 Apr 2023 09:58:19 +0800
From:   Jianhua Lu <lujianhua000@...il.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Neil Armstrong <neil.armstrong@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] drm/panel: nt36523: Add DCS backlight support

On Wed, Apr 12, 2023 at 09:46:00PM +0200, Konrad Dybcio wrote:
> This chip supports controlling the backlight via DCS commands, on at
> least some panels. Add support for doing so.
> 
> Note this may only concern the NT36523*W* variant. Nobody knows, really,
> there's no docs.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  drivers/gpu/drm/panel/panel-novatek-nt36523.c | 67 +++++++++++++++++++++++++--
>  1 file changed, 64 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-novatek-nt36523.c b/drivers/gpu/drm/panel/panel-novatek-nt36523.c
> index d30dbbfb67b1..3c81ec014eef 100644
> --- a/drivers/gpu/drm/panel/panel-novatek-nt36523.c
> +++ b/drivers/gpu/drm/panel/panel-novatek-nt36523.c
> @@ -5,6 +5,7 @@
>   * Copyright (c) 2022, 2023 Jianhua Lu <lujianhua000@...il.com>
>   */
>  
> +
[..]
> +static struct backlight_device *nt36523_create_backlight(struct mipi_dsi_device *dsi)
> +{
> +	struct device *dev = &dsi->dev;
> +	const struct backlight_properties props = {
> +		.type = BACKLIGHT_RAW,
> +		.brightness = 512,
> +		.max_brightness = 4095,
Please set the missing scale property of backlight. Daniel said: "Unknown is never correct for
new drivers."
See https://lore.kernel.org/lkml/Y6SIWoVFX%2FOlNO0n@aspen.lan/

Otherwise,

Reviewed-by: Jianhua Lu <lujianhua000@...il.com>
> +	};
> +
> +	return devm_backlight_device_register(dev, dev_name(dev), dev, dsi,
> +					      &nt36523_bl_ops, &props);
> +}
> +
>  static int nt36523_probe(struct mipi_dsi_device *dsi)
>  {
>  	struct device *dev = &dsi->dev;
> @@ -730,9 +784,16 @@ static int nt36523_probe(struct mipi_dsi_device *dsi)
>  	mipi_dsi_set_drvdata(dsi, pinfo);
>  	drm_panel_init(&pinfo->panel, dev, &nt36523_panel_funcs, DRM_MODE_CONNECTOR_DSI);
>  
> -	ret = drm_panel_of_backlight(&pinfo->panel);
> -	if (ret)
> -		return dev_err_probe(dev, ret, "failed to get backlight\n");
> +	if (pinfo->desc->has_dcs_backlight) {
> +		pinfo->panel.backlight = nt36523_create_backlight(dsi);
> +		if (IS_ERR(pinfo->panel.backlight))
> +			return dev_err_probe(dev, PTR_ERR(pinfo->panel.backlight),
> +					     "Failed to create backlight\n");
> +	} else {
> +		ret = drm_panel_of_backlight(&pinfo->panel);
> +		if (ret)
> +			return dev_err_probe(dev, ret, "Failed to get backlight\n");
> +	}
>  
>  	drm_panel_add(&pinfo->panel);
>  
> 
> -- 
> 2.40.0
>