drm/sysfb: Blit to CRTC destination format

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 input 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,
displaying XRGB8888-based buffers under C8 can be achieved.

v2:
- refer to RGB332 as CRTC input format

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250714151513.309475-5-tzimmermann@suse.de

Author: tdz

drivers/gpu/drm/sysfb/drm_sysfb_helper.h

@@ -132,7 +132,7 @@ 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 input color format; required for color mgmt. */
 	const struct drm_format_info *format;
 };
 

drivers/gpu/drm/sysfb/drm_sysfb_modeset.c

@@ -210,7 +210,12 @@ 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 */
@@ -220,11 +225,6 @@ 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);
@@ -238,7 +238,10 @@ 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;
@@ -278,7 +281,10 @@ 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;
@@ -370,16 +376,19 @@ 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);