linux-kernel - Re: [PATCH RFC v1] drm/meson: venc: add support for HDMI DMT modes up to 3840x2160

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Message-ID: <aac69070-d000-460f-a1fc-4ac5c097c7e5@linaro.org>
Date: Mon, 5 Jan 2026 15:52:11 +0100
From: neil.armstrong@...aro.org
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 linux-amlogic@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de,
 tobetter@...il.com, christianshewitt@...il.com
Subject: Re: [PATCH RFC v1] drm/meson: venc: add support for HDMI DMT modes up
 to 3840x2160

On 11/8/25 14:42, Martin Blumenstingl wrote:
> Commit 5d0bfe448481 ("drm/meson: Add HDMI 1.4 4k modes") added support
> for HDMI 1.4 4k modes, which is what TVs need. For computer monitors
> the code is using the DMT code-path, which ends up in
> meson_venc_hdmi_supported_mode(), which does not allow the 4k modes yet.
> 
> The datasheet for all supported SoCs mentions "4Kx2K@60". It's not
> clear whether "4K" here means 3840 or 4096 pixels.
> 
> Allow resolutions up to 3840x2160 pixels (including middle steps, such
> as WQHD at 2560x1440 pixels) so they can be used with computer monitors
> (using the DMT code-path in the driver).
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
> I'm sending this as RFC as I'm hoping to get some comments on the
> "4Kx2K@60" note from the datasheets.
> 
> I have tested it myself on a GXL Le Potato board using a computer
> monitor at 2560x1440 pixels.
> 
> This is the spiritual successor of a patch titled "drm/meson: add
> support for 2560x1440 resolution output" from [0]
> 
> [0] https://lore.kernel.org/linux-amlogic/20250927130239.825060-1-christianshewitt@gmail.com/
> 
> 
>   drivers/gpu/drm/meson/meson_venc.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_venc.c b/drivers/gpu/drm/meson/meson_venc.c
> index 3bf0d6e4fc30..4abd0c09b442 100644
> --- a/drivers/gpu/drm/meson/meson_venc.c
> +++ b/drivers/gpu/drm/meson/meson_venc.c
> @@ -868,10 +868,10 @@ meson_venc_hdmi_supported_mode(const struct drm_display_mode *mode)
>   			    DRM_MODE_FLAG_PVSYNC | DRM_MODE_FLAG_NVSYNC))
>   		return MODE_BAD;
>   
> -	if (mode->hdisplay < 400 || mode->hdisplay > 1920)
> +	if (mode->hdisplay < 400 || mode->hdisplay > 3840)
>   		return MODE_BAD_HVALUE;
>   
> -	if (mode->vdisplay < 480 || mode->vdisplay > 1920)
> +	if (mode->vdisplay < 480 || mode->vdisplay > 2160)
>   		return MODE_BAD_VVALUE;
>   
>   	return MODE_OK;

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

Thanks,
Neil