drm/sysfb: Lookup blit function during atomic check

Some configurations of sysfb outputs require format conversion from
framebuffer to scanout buffer. It is a driver bug if the conversion
helper is missing, yet it might happen on odd scanout formats. The old
code, based on drm_fb_blit(), only detects this situation during the
commit's hardware update, which is too late to abort the update.

Lookup the correct blit helper as part of the check phase. Then store
it in the sysfb plane state. Allows for detection of a missing helper
before the commit has started. Also avoids drm_fb_blit()'s large switch
statement on each updated scanline. Only a single lookup has to be done.

The lookup is in drm_sysfb_get_blit_func(), which only tracks formats
supported by sysfb drivers.

The lookup happens in sysfb's begin_fb_access helper instead of its
atomic_check helper. This allows vesadrm, and possibly other drivers,
to implement their own atomic_check without interfering with blit
lookups. Vesadrm implements XRGB8888 on top of R8 formats with the
help of the atomic_check. Doing the blit lookup in begin_fb_access then
always uses the correct CRTC format on all drivers.

v2:
- vesadrm: use drm_sysfb_plane_helper_begin_fb_access()
- fix type in commit description (Javier)

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/sysfb/drm_sysfb_helper.h

···
 struct drm_scanout_buffer;
 struct screen_info;
 
+typedef void (*drm_sysfb_blit_func)(struct iosys_map *, const unsigned int *,
+				    const struct iosys_map *,
+				    const struct drm_framebuffer *,
+				    const struct drm_rect *,
+				    struct drm_format_conv_state *);
+
 /*
  * Input parsing
  */
···
 
 struct drm_sysfb_plane_state {
 	struct drm_shadow_plane_state base;
+
+	/* transfers framebuffer data to scanout buffer in CRTC format */
+	drm_sysfb_blit_func blit_to_crtc;
 };
 
 static inline struct drm_sysfb_plane_state *
···
 				   const u32 *native_fourccs, size_t native_nfourccs,
 				   u32 *fourccs_out, size_t nfourccs_out);
 
+int drm_sysfb_plane_helper_begin_fb_access(struct drm_plane *plane,
+					   struct drm_plane_state *plane_state);
 int drm_sysfb_plane_helper_atomic_check(struct drm_plane *plane,
 					struct drm_atomic_state *new_state);
 void drm_sysfb_plane_helper_atomic_update(struct drm_plane *plane,
···
 	DRM_FORMAT_MOD_INVALID
 
 #define DRM_SYSFB_PLANE_HELPER_FUNCS \
-	DRM_GEM_SHADOW_PLANE_HELPER_FUNCS, \
+	.begin_fb_access = drm_sysfb_plane_helper_begin_fb_access, \
+	.end_fb_access = drm_gem_end_shadow_fb_access, \
 	.atomic_check = drm_sysfb_plane_helper_atomic_check, \
 	.atomic_update = drm_sysfb_plane_helper_atomic_update, \
 	.atomic_disable = drm_sysfb_plane_helper_atomic_disable, \

drivers/gpu/drm/sysfb/drm_sysfb_modeset.c

···
 	kfree(sysfb_plane_state);
 }
 
+static void drm_sysfb_memcpy(struct iosys_map *dst, const unsigned int *dst_pitch,
+			     const struct iosys_map *src, const struct drm_framebuffer *fb,
+			     const struct drm_rect *clip, struct drm_format_conv_state *state)
+{
+	drm_fb_memcpy(dst, dst_pitch, src, fb, clip);
+}
+
+static drm_sysfb_blit_func drm_sysfb_get_blit_func(u32 dst_format, u32 src_format)
+{
+	if (src_format == dst_format) {
+		return drm_sysfb_memcpy;
+	} else if (src_format == DRM_FORMAT_XRGB8888) {
+		switch (dst_format) {
+		case DRM_FORMAT_RGB565:
+			return drm_fb_xrgb8888_to_rgb565;
+		case DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN:
+			return drm_fb_xrgb8888_to_rgb565be;
+		case DRM_FORMAT_XRGB1555:
+			return drm_fb_xrgb8888_to_xrgb1555;
+		case DRM_FORMAT_ARGB1555:
+			return drm_fb_xrgb8888_to_argb1555;
+		case DRM_FORMAT_RGBA5551:
+			return drm_fb_xrgb8888_to_rgba5551;
+		case DRM_FORMAT_RGB888:
+			return drm_fb_xrgb8888_to_rgb888;
+		case DRM_FORMAT_BGR888:
+			return drm_fb_xrgb8888_to_bgr888;
+		case DRM_FORMAT_ARGB8888:
+			return drm_fb_xrgb8888_to_argb8888;
+		case DRM_FORMAT_XBGR8888:
+			return drm_fb_xrgb8888_to_xbgr8888;
+		case DRM_FORMAT_ABGR8888:
+			return drm_fb_xrgb8888_to_abgr8888;
+		case DRM_FORMAT_XRGB2101010:
+			return drm_fb_xrgb8888_to_xrgb2101010;
+		case DRM_FORMAT_ARGB2101010:
+			return drm_fb_xrgb8888_to_argb2101010;
+		case DRM_FORMAT_BGRX8888:
+			return drm_fb_xrgb8888_to_bgrx8888;
+		case DRM_FORMAT_RGB332:
+			return drm_fb_xrgb8888_to_rgb332;
+		}
+	}
+
+	return NULL;
+}
+
+int drm_sysfb_plane_helper_begin_fb_access(struct drm_plane *plane,
+					   struct drm_plane_state *plane_state)
+{
+	struct drm_device *dev = plane->dev;
+	struct drm_sysfb_plane_state *sysfb_plane_state = to_drm_sysfb_plane_state(plane_state);
+	struct drm_framebuffer *fb = plane_state->fb;
+	struct drm_crtc_state *crtc_state;
+	struct drm_sysfb_crtc_state *sysfb_crtc_state;
+	drm_sysfb_blit_func blit_to_crtc;
+	int ret;
+
+	ret = drm_gem_begin_shadow_fb_access(plane, plane_state);
+	if (ret)
+		return ret;
+
+	if (!fb)
+		return 0;
+
+	ret = -EINVAL;
+
+	crtc_state = drm_atomic_get_crtc_state(plane_state->state, plane_state->crtc);
+	if (drm_WARN_ON_ONCE(dev, !crtc_state))
+		goto err_drm_gem_end_shadow_fb_access;
+	sysfb_crtc_state = to_drm_sysfb_crtc_state(crtc_state);
+
+	if (drm_WARN_ON_ONCE(dev, !sysfb_crtc_state->format))
+		goto err_drm_gem_end_shadow_fb_access;
+	blit_to_crtc = drm_sysfb_get_blit_func(sysfb_crtc_state->format->format,
+					       fb->format->format);
+	if (!blit_to_crtc) {
+		drm_warn_once(dev, "No blit helper from %p4cc to %p4cc found.\n",
+			      &fb->format->format, &sysfb_crtc_state->format->format);
+		goto err_drm_gem_end_shadow_fb_access;
+	}
+	sysfb_plane_state->blit_to_crtc = blit_to_crtc;
+
+	return 0;
+
+err_drm_gem_end_shadow_fb_access:
+	drm_gem_end_shadow_fb_access(plane, plane_state);
+	return ret;
+}
+EXPORT_SYMBOL(drm_sysfb_plane_helper_begin_fb_access);
+
 int drm_sysfb_plane_helper_atomic_check(struct drm_plane *plane,
 					struct drm_atomic_state *new_state)
 {
···
 	struct drm_sysfb_device *sysfb = to_drm_sysfb_device(dev);
 	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
 	struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
-	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
+	struct drm_sysfb_plane_state *sysfb_plane_state = to_drm_sysfb_plane_state(plane_state);
+	struct drm_shadow_plane_state *shadow_plane_state = &sysfb_plane_state->base;
 	struct drm_framebuffer *fb = plane_state->fb;
 	unsigned int dst_pitch = sysfb->fb_pitch;
 	struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, plane_state->crtc);
 	struct drm_sysfb_crtc_state *sysfb_crtc_state = to_drm_sysfb_crtc_state(crtc_state);
 	const struct drm_format_info *dst_format = sysfb_crtc_state->format;
+	drm_sysfb_blit_func blit_to_crtc = sysfb_plane_state->blit_to_crtc;
 	struct drm_atomic_helper_damage_iter iter;
 	struct drm_rect damage;
 	int ret, idx;
···
 			continue;
 
 		iosys_map_incr(&dst, drm_fb_clip_offset(dst_pitch, dst_format, &dst_clip));
-		drm_fb_blit(&dst, &dst_pitch, dst_format->format, shadow_plane_state->data, fb,
-			    &damage, &shadow_plane_state->fmtcnv_state);
+		blit_to_crtc(&dst, &dst_pitch, shadow_plane_state->data, fb, &damage,
+			     &shadow_plane_state->fmtcnv_state);
 	}
 
 	drm_dev_exit(idx);
···
 {
 	struct drm_device *dev = plane->dev;
 	struct drm_plane_state *plane_state = plane->state;
+	struct drm_sysfb_plane_state *sysfb_plane_state;
 	struct drm_sysfb_plane_state *new_sysfb_plane_state;
 	struct drm_shadow_plane_state *new_shadow_plane_state;
 
 	if (drm_WARN_ON(dev, !plane_state))
 		return NULL;
+	sysfb_plane_state = to_drm_sysfb_plane_state(plane_state);
 
 	new_sysfb_plane_state = kzalloc(sizeof(*new_sysfb_plane_state), GFP_KERNEL);
 	if (!new_sysfb_plane_state)
···
 	new_shadow_plane_state = &new_sysfb_plane_state->base;
 
 	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
+	new_sysfb_plane_state->blit_to_crtc = sysfb_plane_state->blit_to_crtc;
 
 	return &new_shadow_plane_state->base;
 }

drivers/gpu/drm/sysfb/vesadrm.c

···
 }
 
 static const struct drm_plane_helper_funcs vesadrm_primary_plane_helper_funcs = {
-	DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
+	.begin_fb_access = drm_sysfb_plane_helper_begin_fb_access,
+	.end_fb_access = drm_gem_end_shadow_fb_access,
 	.atomic_check = vesadrm_primary_plane_helper_atomic_check,
 	.atomic_update = drm_sysfb_plane_helper_atomic_update,
 	.atomic_disable = drm_sysfb_plane_helper_atomic_disable,