Each video mode's primary plane requires a minimum amount of video
memory. For double buffering, this is at most half the available
VRAM. Check this constraint.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/gpu/drm/ast/ast_main.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 3a9b4cb73f2f..48d57ab42955 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -387,8 +387,31 @@ static int ast_get_dram_info(struct drm_device *dev)
return 0;
}
+enum drm_mode_status ast_mode_config_mode_valid(struct drm_device *dev,
+ const struct drm_display_mode *mode)
+{
+ static const unsigned long max_bpp = 4; /* DRM_FORMAT_XRGBA8888 */
+
+ struct ast_private *ast = dev->dev_private;
+ unsigned long fbsize, fbpages, max_fbpages;
+
+ /* To support double buffering, a framebuffer may not
+ * consume more than half of the available VRAM.
+ */
+ max_fbpages = (ast->vram_size / 2) >> PAGE_SHIFT;
+
+ fbsize = mode->hdisplay * mode->vdisplay * max_bpp;
+ fbpages = DIV_ROUND_UP(fbsize, PAGE_SIZE);
+
+ if (fbpages > max_fbpages)
+ return MODE_MEM;
+
+ return MODE_OK;
+}
+
static const struct drm_mode_config_funcs ast_mode_funcs = {
- .fb_create = drm_gem_fb_create
+ .fb_create = drm_gem_fb_create,
+ .mode_valid = ast_mode_config_mode_valid,
};
static u32 ast_get_vram_info(struct drm_device *dev)
--
2.23.0
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