Re: [PATCH v2 5/8] drm/rockchip: vop2: Enforce AFBC source alignment in plane_check

From: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
To: "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>
Cc: kernel@collabora.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>
Subject: Re: [PATCH v2 5/8] drm/rockchip: vop2: Enforce AFBC source alignment in plane_check
Date: Mon, 08 Dec 2025 08:24:52 +0100	[thread overview]
Message-ID: <4696988.LvFx2qVVIh@workhorse> (raw)
In-Reply-To: <f9f7b446-8575-4f16-aa96-5197b22846e3@rock-chips.com>

On Monday, 8 December 2025 03:48:24 Central European Standard Time Chaoyi Chen wrote:
> Hello Nicolas, Daniel,
> 
> On 12/7/2025 4:45 AM, Nicolas Frattaroli wrote:
> > From: Daniel Stone <daniels@collabora.com>
> > 
> > Planes can only source AFBC framebuffers at multiples of 4px wide on
> > RK3566/RK3568. Instead of clipping on all SoCs when the user asks for an
> > unaligned source rectangle, reject the configuration in the plane's
> > atomic check on RK3566/RK3568 only.
> > 
> > Signed-off-by: Daniel Stone <daniels@collabora.com>
> > [Make RK3566/RK3568 specific, reword message]
> > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> > ---
> >  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > index bc1ed0ffede0..e23213337104 100644
> > --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > @@ -1076,6 +1076,13 @@ static int vop2_plane_atomic_check(struct drm_plane *plane,
> >  		return -EINVAL;
> >  	}
> >  
> > +	if (vop2->version == VOP_VERSION_RK3568 && drm_is_afbc(fb->modifier) && src_w % 4) {
> > +		drm_dbg_kms(vop2->drm,
> > +			    "AFBC source rectangles must be 4-byte aligned; is %d\n",
> > +			    src_w);
> > +		return -EINVAL;
> > +	}
> > +
> >  	return 0;
> >  }
> >  
> > @@ -1237,11 +1244,8 @@ static void vop2_plane_atomic_update(struct drm_plane *plane,
> >  	WARN_ON(src_w < 4);
> >  	WARN_ON(src_h < 4);
> >  
> > -	if (afbc_en && src_w % 4) {
> > -		drm_dbg_kms(vop2->drm, "vp%d %s src_w[%d] not 4 pixel aligned\n",
> > -			    vp->id, win->data->name, src_w);
> > -		src_w = ALIGN_DOWN(src_w, 4);
> > -	}
> > +	if (vop2->version == VOP_VERSION_RK3568 && drm_is_afbc(fb->modifier))
> > +		WARN_ON(src_w % 4);
> >  
> >  	act_info = (src_h - 1) << 16 | ((src_w - 1) & 0xffff);
> >  	dsp_info = (dsp_h - 1) << 16 | ((dsp_w - 1) & 0xffff);
> > 
> 
> You haven't replied to Andy's comment yet [0].
> 
> [0] https://lore.kernel.org/dri-devel/7b4e26ec.75f3.19a77276b53.Coremail.andyshrk@163.com/
> 

Hello,

I addressed the follow-ups where it was clarified that the 4 pixel
limitation was RK3566/RK3568-only. I'm not going to bring back the
post-atomic_check modification for a fast path, but I'm open to
suggestions on how to do this differently.

One solution might be to modify the state with the ALIGN_DOWN stuff
in atomic_check instead, where userspace is then aware of the change
being done to its requested parameters. I'll need to double-check
whether this is in line with atomic modesetting's design.

Kind regards,
Nicolas Frattaroli