[PATCH 4/9] drm/sysfb: Blit to CRTC destination format

Thomas Zimmermann tzimmermann at suse.de
Tue Jun 17 14:23:16 UTC 2025


Use the color format stored in struct drm_sysfb_crtc_state for
color-format conversion instead of the scanout-buffer format
announced by firmware. Currently, both values are identical.

This will allow drivers to modify the CRTC's output format to a
certain extend. Specifically, vesadrm will be able to display RGB
framebuffers when the scanout buffer is of C8 format. With color-
format conversion to RGB332 and correct setup of the C8 palette,
output of XRGB8888-based buffers can be achieved.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
---
 drivers/gpu/drm/sysfb/drm_sysfb_helper.h  |  2 +-
 drivers/gpu/drm/sysfb/drm_sysfb_modeset.c | 29 +++++++++++++++--------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
index cb08a88242cc..39704953d2d4 100644
--- a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
+++ b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
@@ -128,7 +128,7 @@ int drm_sysfb_plane_helper_get_scanout_buffer(struct drm_plane *plane,
 struct drm_sysfb_crtc_state {
 	struct drm_crtc_state base;
 
-	/* Primary-plane format; required for color mgmt. */
+	/* CRTC output color format; required for color mgmt. */
 	const struct drm_format_info *format;
 };
 
diff --git a/drivers/gpu/drm/sysfb/drm_sysfb_modeset.c b/drivers/gpu/drm/sysfb/drm_sysfb_modeset.c
index ffaa2522ab96..d79ac285ac43 100644
--- a/drivers/gpu/drm/sysfb/drm_sysfb_modeset.c
+++ b/drivers/gpu/drm/sysfb/drm_sysfb_modeset.c
@@ -72,7 +72,12 @@ int drm_sysfb_plane_helper_atomic_check(struct drm_plane *plane,
 	else if (!new_plane_state->visible)
 		return 0;
 
-	if (new_fb->format != sysfb->fb_format) {
+	new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_plane_state->crtc);
+
+	new_sysfb_crtc_state = to_drm_sysfb_crtc_state(new_crtc_state);
+	new_sysfb_crtc_state->format = sysfb->fb_format;
+
+	if (new_fb->format != new_sysfb_crtc_state->format) {
 		void *buf;
 
 		/* format conversion necessary; reserve buffer */
@@ -82,11 +87,6 @@ int drm_sysfb_plane_helper_atomic_check(struct drm_plane *plane,
 			return -ENOMEM;
 	}
 
-	new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_plane_state->crtc);
-
-	new_sysfb_crtc_state = to_drm_sysfb_crtc_state(new_crtc_state);
-	new_sysfb_crtc_state->format = new_fb->format;
-
 	return 0;
 }
 EXPORT_SYMBOL(drm_sysfb_plane_helper_atomic_check);
@@ -100,7 +100,10 @@ void drm_sysfb_plane_helper_atomic_update(struct drm_plane *plane, struct drm_at
 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
 	struct drm_framebuffer *fb = plane_state->fb;
 	unsigned int dst_pitch = sysfb->fb_pitch;
-	const struct drm_format_info *dst_format = sysfb->fb_format;
+	struct drm_crtc_state *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;
 	struct drm_atomic_helper_damage_iter iter;
 	struct drm_rect damage;
 	int ret, idx;
@@ -140,7 +143,10 @@ void drm_sysfb_plane_helper_atomic_disable(struct drm_plane *plane,
 	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
 	void __iomem *dst_vmap = dst.vaddr_iomem; /* TODO: Use mapping abstraction */
 	unsigned int dst_pitch = sysfb->fb_pitch;
-	const struct drm_format_info *dst_format = sysfb->fb_format;
+	struct drm_crtc_state *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;
 	struct drm_rect dst_clip;
 	unsigned long lines, linepixels, i;
 	int idx;
@@ -232,16 +238,19 @@ EXPORT_SYMBOL(drm_sysfb_crtc_helper_atomic_check);
 
 void drm_sysfb_crtc_reset(struct drm_crtc *crtc)
 {
+	struct drm_sysfb_device *sysfb = to_drm_sysfb_device(crtc->dev);
 	struct drm_sysfb_crtc_state *sysfb_crtc_state;
 
 	if (crtc->state)
 		drm_sysfb_crtc_state_destroy(to_drm_sysfb_crtc_state(crtc->state));
 
 	sysfb_crtc_state = kzalloc(sizeof(*sysfb_crtc_state), GFP_KERNEL);
-	if (sysfb_crtc_state)
+	if (sysfb_crtc_state) {
+		sysfb_crtc_state->format = sysfb->fb_format;
 		__drm_atomic_helper_crtc_reset(crtc, &sysfb_crtc_state->base);
-	else
+	} else {
 		__drm_atomic_helper_crtc_reset(crtc, NULL);
+	}
 }
 EXPORT_SYMBOL(drm_sysfb_crtc_reset);
 
-- 
2.49.0



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