linux-kernel - Re: [PATCH v2] drm/rockchip: vop2: Add mode valid callback for crtc

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Message-ID: <aW1uWZD6u4e2o6jF@venus>
Date: Mon, 19 Jan 2026 00:43:35 +0100
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: Andy Yan <andyshrk@....com>
Cc: heiko@...ech.de, hjc@...k-chips.com, mripard@...nel.org, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org, Andy Yan <andy.yan@...k-chips.com>
Subject: Re: [PATCH v2] drm/rockchip: vop2: Add mode valid callback for crtc

Hi,

On Sat, Jan 17, 2026 at 10:07:30AM +0800, Andy Yan wrote:
> From: Andy Yan <andy.yan@...k-chips.com>
> 
> The different Video Ports support different maximum resolutions.
> Reject resolutions that are not supported by a specific VP.
> 
> Only the output width is checked because the hardware itself does
> not have a hard output height limit.
> 
> Filter the mode that can't output by the VP/crtc.
> 
> Signed-off-by: Andy Yan <andy.yan@...k-chips.com>
> 
> ---

A common RK3576 setup is VP0 mapped to HDMI and VP1 mapped to USB-C
DP AltMode. Since RK3576 VP1 only supports 2.5K, this can easily
become relevant when connecting a 4K screen via USB-C DP AltMode.
I've tested that this patch properly drops all unsupported modes
based on the resolution.

Further checks will be needed to ensure the bandwidth requirements
are also met (e.g. RK3576 VP1 only supports 2.5K@...z, so 2.5K@...Hz
should be marked as BAD). I think the bandwidth check should be a
separate patch, but thought it might be worth mentioning here in
case somebody stumbles over it.

Anyways:

Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>
Tested-by: Sebastian Reichel <sebastian.reichel@...labora.com> # Sige5

Greetings,

-- Sebastian

> 
> Changes in v2:
> - Add more detailed commit message
> 
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> index 498df0ce4680..74fba29bfff3 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> @@ -1439,6 +1439,17 @@ static void vop2_crtc_disable_vblank(struct drm_crtc *crtc)
>  	vop2_crtc_disable_irq(vp, VP_INT_FS_FIELD);
>  }
>  
> +static enum drm_mode_status vop2_crtc_mode_valid(struct drm_crtc *crtc,
> +						 const struct drm_display_mode *mode)
> +{
> +	struct vop2_video_port *vp = to_vop2_video_port(crtc);
> +
> +	if (mode->hdisplay > vp->data->max_output.width)
> +		return MODE_BAD_HVALUE;
> +
> +	return MODE_OK;
> +}
> +
>  static bool vop2_crtc_mode_fixup(struct drm_crtc *crtc,
>  				 const struct drm_display_mode *mode,
>  				 struct drm_display_mode *adj_mode)
> @@ -1884,6 +1895,7 @@ static void vop2_crtc_atomic_flush(struct drm_crtc *crtc,
>  
>  static const struct drm_crtc_helper_funcs vop2_crtc_helper_funcs = {
>  	.mode_fixup = vop2_crtc_mode_fixup,
> +	.mode_valid = vop2_crtc_mode_valid,
>  	.atomic_check = vop2_crtc_atomic_check,
>  	.atomic_begin = vop2_crtc_atomic_begin,
>  	.atomic_flush = vop2_crtc_atomic_flush,
> -- 
> 2.43.0
> 
> base-commit: 1613a67b5360d6ff78f62143a1cf123414a1b4d9
> branch: rk3576-dp-upstream
> 

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