linux-kernel - Re: [RFC PATCH v3 3/3] drm/panel: vtdr6130: Use 16-bit brightness function

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Message-ID: <47b70ca1-2601-0e71-80bd-6d3f3f845601@linaro.org>
Date:   Wed, 18 Jan 2023 10:45:30 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Richard Acayan <mailingradian@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Vinay Simha BN <simhavcs@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Daniel Mentz <danielmentz@...gle.com>,
        Caleb Connolly <caleb@...nolly.tech>
Subject: Re: [RFC PATCH v3 3/3] drm/panel: vtdr6130: Use 16-bit brightness
 function

On 16/01/2023 23:49, Richard Acayan wrote:
> This panel communicates brightness in big endian. This is not a quirk of
> the panels themselves, but rather, a part of the MIPI standard. Use the
> new mipi_dsi_dcs_set_display_brightness_large() function that properly
> handles 16-bit brightness instead of bypassing the brightness functions
> entirely.
> 
> Signed-off-by: Richard Acayan <mailingradian@...il.com>
> ---
>   drivers/gpu/drm/panel/panel-visionox-vtdr6130.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> index f9a6abc1e121..1092075b31a5 100644
> --- a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> +++ b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> @@ -243,12 +243,9 @@ static int visionox_vtdr6130_bl_update_status(struct backlight_device *bl)
>   {
>   	struct mipi_dsi_device *dsi = bl_get_data(bl);
>   	u16 brightness = backlight_get_brightness(bl);
> -	/* Panel needs big-endian order of brightness value */
> -	u8 payload[2] = { brightness >> 8, brightness & 0xff };
>   	int ret;
>   
> -	ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
> -				 payload, sizeof(payload));
> +	mipi_dsi_dcs_set_display_brightness_large(dsi, brightness);
>   	if (ret < 0)
>   		return ret;
>   

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
Tested-by: Neil Armstrong <neil.armstrong@...aro.org> # on SM8550-MTP

Thanks !