drm/cirrus-qemu: Use framebuffer format as-is, drop adjustments

Remove internal adjustments to framebuffer format from cirrus-qemu
driver. The driver did this to support higher resolutions by reducing
the per-pixel memory consumption. DRM has a policy of exporting formats
as they are implemented in hardware. So avoid internal adjustments if
possible.

Also remove the call to drm_fb_blit() from cirrus-qemu. The helper
is useful if source and destination format are not known beforehand.
This is not the case for cirrus-qemu.

This change effectively reduces the maximum available resolution to
800x600 at 32 bpp. A maximum scanline pitch of 4095 byte prevents
1024 pixels per scanline at 32 bpp. Higher resolutions are possible
at lower bit depths, but are currently not supported by userspace.

When cirrus-qemu currently reduced the internal bit depth to support
higher resolutions, it trades resolution for bit depth and CPU time.
Converting from 32-bit colors has a significant runtime overhead, as
outlined at [1]. Avoiding color-format adjustments also avoids this
tradeoff.

v2:
- expand commit message (Gerd)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://lore.kernel.org/dri-devel/20250325110407.81107-1-tzimmermann@suse.de/
Link: https://lore.kernel.org/r/20250328091821.195061-4-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/tiny/cirrus-qemu.c b/drivers/gpu/drm/tiny/cirrus-qemu.c
index 0306433ec117ccea8ee7e4421cc60b7893a57b66..76744394e2a3b21b14a2921c9c686e57e8649da0 100644 (file)
--- a/drivers/gpu/drm/tiny/cirrus-qemu.c
+++ b/drivers/gpu/drm/tiny/cirrus-qemu.c
@@ -72,10 +72,6 @@ struct cirrus_device {
 
 struct cirrus_primary_plane_state {
        struct drm_shadow_plane_state base;
-
-       /* HW scanout buffer */
-       const struct drm_format_info   *format;
-       unsigned int                   pitch;
 };
 
 static inline struct cirrus_primary_plane_state *
@@ -144,37 +140,6 @@ static void wreg_hdr(struct cirrus_device *cirrus, u8 val)
        iowrite8(val, cirrus->mmio + VGA_DAC_MASK);
 }
 
-static const struct drm_format_info *cirrus_convert_to(struct drm_framebuffer *fb)
-{
-       if (fb->format->format == DRM_FORMAT_XRGB8888 && fb->pitches[0] > CIRRUS_MAX_PITCH) {
-               if (fb->width * 3 <= CIRRUS_MAX_PITCH)
-                       /* convert from XR24 to RG24 */
-                       return drm_format_info(DRM_FORMAT_RGB888);
-               else
-                       /* convert from XR24 to RG16 */
-                       return drm_format_info(DRM_FORMAT_RGB565);
-       }
-       return NULL;
-}
-
-static const struct drm_format_info *cirrus_format(struct drm_framebuffer *fb)
-{
-       const struct drm_format_info *format = cirrus_convert_to(fb);
-
-       if (format)
-               return format;
-       return fb->format;
-}
-
-static int cirrus_pitch(struct drm_framebuffer *fb)
-{
-       const struct drm_format_info *format = cirrus_convert_to(fb);
-
-       if (format)
-               return drm_format_info_min_pitch(format, 0, fb->width);
-       return fb->pitches[0];
-}
-
 static void cirrus_set_start_address(struct cirrus_device *cirrus, u32 offset)
 {
        u32 addr;
@@ -341,13 +306,10 @@ static int cirrus_primary_plane_helper_atomic_check(struct drm_plane *plane,
                                                    struct drm_atomic_state *state)
 {
        struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state, plane);
-       struct cirrus_primary_plane_state *new_primary_plane_state =
-               to_cirrus_primary_plane_state(new_plane_state);
        struct drm_framebuffer *fb = new_plane_state->fb;
        struct drm_crtc *new_crtc = new_plane_state->crtc;
        struct drm_crtc_state *new_crtc_state = NULL;
        int ret;
-       unsigned int pitch;
 
        if (new_crtc)
                new_crtc_state = drm_atomic_get_new_crtc_state(state, new_crtc);
@@ -361,17 +323,12 @@ static int cirrus_primary_plane_helper_atomic_check(struct drm_plane *plane,
        else if (!new_plane_state->visible)
                return 0;
 
-       pitch = cirrus_pitch(fb);
-
        /* validate size constraints */
-       if (pitch > CIRRUS_MAX_PITCH)
+       if (fb->pitches[0] > CIRRUS_MAX_PITCH)
                return -EINVAL;
-       else if (pitch * fb->height > CIRRUS_VRAM_SIZE)
+       else if (fb->pitches[0] > CIRRUS_VRAM_SIZE / fb->height)
                return -EINVAL;
 
-       new_primary_plane_state->format = cirrus_format(fb);
-       new_primary_plane_state->pitch = pitch;
-
        return 0;
 }
 
@@ -380,15 +337,10 @@ static void cirrus_primary_plane_helper_atomic_update(struct drm_plane *plane,
 {
        struct cirrus_device *cirrus = to_cirrus(plane->dev);
        struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
-       struct cirrus_primary_plane_state *primary_plane_state =
-               to_cirrus_primary_plane_state(plane_state);
        struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
        struct drm_framebuffer *fb = plane_state->fb;
-       const struct drm_format_info *format = primary_plane_state->format;
-       unsigned int pitch = primary_plane_state->pitch;
        struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
-       struct cirrus_primary_plane_state *old_primary_plane_state =
-               to_cirrus_primary_plane_state(old_plane_state);
+       struct drm_framebuffer *old_fb = old_plane_state->fb;
        struct iosys_map vaddr = IOSYS_MAP_INIT_VADDR_IOMEM(cirrus->vram);
        struct drm_atomic_helper_damage_iter iter;
        struct drm_rect damage;
@@ -400,18 +352,17 @@ static void cirrus_primary_plane_helper_atomic_update(struct drm_plane *plane,
        if (!drm_dev_enter(&cirrus->dev, &idx))
                return;
 
-       if (old_primary_plane_state->format != format)
-               cirrus_format_set(cirrus, format);
-       if (old_primary_plane_state->pitch != pitch)
-               cirrus_pitch_set(cirrus, pitch);
+       if (!old_fb || old_fb->format != fb->format)
+               cirrus_format_set(cirrus, fb->format);
+       if (!old_fb || old_fb->pitches[0] != fb->pitches[0])
+               cirrus_pitch_set(cirrus, fb->pitches[0]);
 
        drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
        drm_atomic_for_each_plane_damage(&iter, &damage) {
-               unsigned int offset = drm_fb_clip_offset(pitch, format, &damage);
+               unsigned int offset = drm_fb_clip_offset(fb->pitches[0], fb->format, &damage);
                struct iosys_map dst = IOSYS_MAP_INIT_OFFSET(&vaddr, offset);
 
-               drm_fb_blit(&dst, &pitch, format->format, shadow_plane_state->data, fb,
-                           &damage, &shadow_plane_state->fmtcnv_state);
+               drm_fb_memcpy(&dst, fb->pitches, shadow_plane_state->data, fb, &damage);
        }
 
        drm_dev_exit(idx);
@@ -427,8 +378,6 @@ static struct drm_plane_state *
 cirrus_primary_plane_atomic_duplicate_state(struct drm_plane *plane)
 {
        struct drm_plane_state *plane_state = plane->state;
-       struct cirrus_primary_plane_state *primary_plane_state =
-               to_cirrus_primary_plane_state(plane_state);
        struct cirrus_primary_plane_state *new_primary_plane_state;
        struct drm_shadow_plane_state *new_shadow_plane_state;
 
@@ -441,8 +390,6 @@ cirrus_primary_plane_atomic_duplicate_state(struct drm_plane *plane)
        new_shadow_plane_state = &new_primary_plane_state->base;
 
        __drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
-       new_primary_plane_state->format = primary_plane_state->format;
-       new_primary_plane_state->pitch = primary_plane_state->pitch;
 
        return &new_shadow_plane_state->base;
 }