[PATCH v4] drm/rockchip: Disable AFBC for res >2560 on rk3399

[Andy Yan]

Hi Konstantin,

At 2025-04-17 14:57:58, "Konstantin Shabanov" <mail at etehtsea.me> wrote:
>As it isn't supported by hardware. At least, RK3399 doesn't support
>it. From the datasheet[1]
>("1.2.10 Video IN/OUT", "Display Interface", p. 17):
>
>  Support AFBC function co-operation with GPU
>    * support 2560x1600 UI
>
>Manually tested on RockPro64 (rk3399):
>- ARM_AFBC modifier is used for 1920x1080
>- DRM_FORMAT_MOD_LINEAR modifier us used for 3840x2160
>- No noise on the screen when sway is running in 4k
>- Dynamic resolution switching works correctly in sway
>
>Signed-off-by: Konstantin Shabanov <mail at etehtsea.me>
>Cc: Daniel Stone <daniel at fooishbar.org>
>Cc: Andy Yan <andyshrk at 163.com>
>Reported-by: Dan Callaghan <djc at djc.id.au>
>Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7968
>
>[1]: https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf
>---
>V3 -> V4: Correct redundant header inclusion
>V2 -> V3: Run check only on rk3399
>V1 -> V2: Move the check to the fb_create callback
>
> drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
>diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>index dcc1f07632c3..45e1619b5c97 100644
>--- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>+++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>@@ -5,6 +5,7 @@
>  */
>
> #include <linux/kernel.h>
>+#include <linux/of.h>
>
> #include <drm/drm.h>
> #include <drm/drm_atomic.h>
>@@ -18,6 +19,8 @@
> #include "rockchip_drm_fb.h"
> #include "rockchip_drm_gem.h"
>
>+#define RK3399_AFBC_MAX_WIDTH		2560
>+
> static const struct drm_framebuffer_funcs rockchip_drm_fb_funcs = {
> 	.destroy       = drm_gem_fb_destroy,
> 	.create_handle = drm_gem_fb_create_handle,
>@@ -52,6 +55,15 @@ rockchip_fb_create(struct drm_device *dev, struct drm_file *file,
> 	}
>
> 	if (drm_is_afbc(mode_cmd->modifier[0])) {
>+		if (of_machine_is_compatible("rockchip,rk3399")) {
>+			if (mode_cmd->width > RK3399_AFBC_MAX_WIDTH) {
>+				DRM_DEBUG_KMS("AFBC is not supported for the width %d (max %d)\n",
>+					      mode_cmd->width,
>+					      RK3399_AFBC_MAX_WIDTH);
>+				return ERR_PTR(-EINVAL);
>+			};
>+		}
>+


I prefer the V1 version PATCH[0]. This is because we do not deal with hardware-related
differences at this level.  It involves a VOP-related restriction and we always  handle
limitiation like this  within the VOP driver . 

[0] https://lore.kernel.org/dri-devel/20250402125320.21836-1-mail@etehtsea.me/


> 		int ret, i;
>
> 		ret = drm_gem_fb_afbc_init(dev, mode_cmd, afbc_fb);
>
>base-commit: 4890d68db651562ea80250f2c93205a5c0327a6a
>--
>2.48.1