drm/ast: Swap framebuffer writes on big-endian machines

Swap the pixel data when writing to framebuffer memory on big-endian
machines. Fixes incorrect output. Aspeed graphics does not appear to
support big-endian framebuffers after AST2400, although the feature
has been documented.

There's a lengthy discussion at [1].

v5:
- avoid restricted cast from __be16 (kernel test robot)

Signed-off-by: René Rebe <rene@exactco.de>
Link: https://lore.kernel.org/dri-devel/20251202.170626.2134482663677806825.rene@exactco.de/
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20251212.210504.1355099120650239629.rene@exactco.de

diff --git a/drivers/gpu/drm/ast/ast_cursor.c b/drivers/gpu/drm/ast/ast_cursor.c
index 30b62d3f015133d955bfc61e079fec5acea868dd..3fa8e75db9c0542951ecfb57ee87d6f33c4b2dcc 100644 (file)
--- a/drivers/gpu/drm/ast/ast_cursor.c
+++ b/drivers/gpu/drm/ast/ast_cursor.c
@@ -93,12 +93,17 @@ static void ast_set_cursor_image(struct ast_device *ast, const u8 *src,
                                 unsigned int width, unsigned int height)
 {
        u8 __iomem *dst = ast_plane_vaddr(&ast->cursor_plane.base);
-       u32 csum;
-
-       csum = ast_cursor_calculate_checksum(src, width, height);
+       u32 csum = ast_cursor_calculate_checksum(src, width, height);
 
        /* write pixel data */
+#if defined(__BIG_ENDIAN)
+       unsigned int i;
+
+       for (i = 0; i < AST_HWC_SIZE; i += 2)
+               writew(swab16(*(const __u16 *)&src[i]), &dst[i]);
+#else
        memcpy_toio(dst, src, AST_HWC_SIZE);
+#endif
 
        /* write checksum + signature */
        dst += AST_HWC_SIZE;

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index cd08990a10f936ae56fd9806bb2e20e3106db8af..57c6fbc3232b046cbb912fd1bee00485eb0f8d44 100644 (file)
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -526,12 +526,18 @@ static int ast_primary_plane_helper_atomic_check(struct drm_plane *plane,
 
 static void ast_handle_damage(struct ast_plane *ast_plane, struct iosys_map *src,
                              struct drm_framebuffer *fb,
-                             const struct drm_rect *clip)
+                             const struct drm_rect *clip,
+                             struct drm_format_conv_state *fmtcnv_state)
 {
        struct iosys_map dst = IOSYS_MAP_INIT_VADDR_IOMEM(ast_plane_vaddr(ast_plane));
 
        iosys_map_incr(&dst, drm_fb_clip_offset(fb->pitches[0], fb->format, clip));
+
+#if defined(__BIG_ENDIAN)
+       drm_fb_swab(&dst, fb->pitches, src, fb, clip, !src[0].is_iomem, fmtcnv_state);
+#else
        drm_fb_memcpy(&dst, fb->pitches, src, fb, clip);
+#endif
 }
 
 static void ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
@@ -561,7 +567,8 @@ static void ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
        if (drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE) == 0) {
                drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
                drm_atomic_for_each_plane_damage(&iter, &damage) {
-                       ast_handle_damage(ast_plane, shadow_plane_state->data, fb, &damage);
+                       ast_handle_damage(ast_plane, shadow_plane_state->data, fb, &damage,
+                                         &shadow_plane_state->fmtcnv_state);
                }
 
                drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);