Re: [PATCH v4 2/8] drm/rockchip: vop2: Switch impossible pos conditional to WARN_ON

From: David Laight <david.laight.linux@gmail.com>
To: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Cc: "Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Simona Vetter" <simona@ffwll.ch>,
	"Chaoyi Chen" <chaoyi.chen@rock-chips.com>,
	dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Daniel Stone" <daniels@collabora.com>,
	kernel@collabora.com
Subject: Re: [PATCH v4 2/8] drm/rockchip: vop2: Switch impossible pos conditional to WARN_ON
Date: Thu, 11 Dec 2025 22:41:02 +0000	[thread overview]
Message-ID: <20251211224102.5e079d70@pumpkin> (raw)
In-Reply-To: <20251211-vop2-atomic-fixups-v4-2-5d50eda26bf8@collabora.com>

On Thu, 11 Dec 2025 21:40:32 +0100
Nicolas Frattaroli <nicolas.frattaroli@collabora.com> wrote:

> From: Daniel Stone <daniels@collabora.com>
> 
> We already clip the plane to the display bounds in atomic_check, and
> ensure that it is sufficiently sized. Instead of trying to catch this
> and adjust for it in atomic_update, just assert that atomic_check has
> done its job.
> 
> Signed-off-by: Daniel Stone <daniels@collabora.com>
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 29 +++++++++-------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> index 20b49209ddcd..81b3eba07095 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> @@ -1214,28 +1214,17 @@ static void vop2_plane_atomic_update(struct drm_plane *plane,
>  	src_w = drm_rect_width(src) >> 16;
>  	src_h = drm_rect_height(src) >> 16;
>  	dsp_w = drm_rect_width(dest);
> -
> -	if (dest->x1 + dsp_w > adjusted_mode->hdisplay) {
> -		drm_dbg_kms(vop2->drm,
> -			    "vp%d %s dest->x1[%d] + dsp_w[%d] exceed mode hdisplay[%d]\n",
> -			    vp->id, win->data->name, dest->x1, dsp_w, adjusted_mode->hdisplay);
> -		dsp_w = adjusted_mode->hdisplay - dest->x1;
> -		if (dsp_w < 4)
> -			dsp_w = 4;
> -		src_w = dsp_w * src_w / drm_rect_width(dest);
> -	}
> -
>  	dsp_h = drm_rect_height(dest);
>  
> -	if (dest->y1 + dsp_h > adjusted_mode->vdisplay) {
> -		drm_dbg_kms(vop2->drm,
> -			    "vp%d %s dest->y1[%d] + dsp_h[%d] exceed mode vdisplay[%d]\n",
> -			    vp->id, win->data->name, dest->y1, dsp_h, adjusted_mode->vdisplay);
> -		dsp_h = adjusted_mode->vdisplay - dest->y1;
> -		if (dsp_h < 4)
> -			dsp_h = 4;
> -		src_h = dsp_h * src_h / drm_rect_height(dest);
> -	}
> +	/* drm_atomic_helper_check_plane_state calls drm_rect_clip_scaled for
> +	 * us, which keeps our planes bounded within the CRTC active area
> +	 */
> +	WARN_ON(dest->x1 + dsp_w > adjusted_mode->hdisplay);
> +	WARN_ON(dest->y1 + dsp_h > adjusted_mode->vdisplay);
> +	WARN_ON(dsp_w < 4);
> +	WARN_ON(dsp_h < 4);
> +	WARN_ON(src_w < 4);
> +	WARN_ON(src_h < 4);

You need to do something when the tests fail.
Carrying on regardless is never right.

	David

>  
>  	/*
>  	 * This is workaround solution for IC design:
> 