[PATCH v2 5/7] drm/ast: Add helper for computing framebuffer location in video memory

[Thomas Zimmermann]

The ast driver stores the primary plane's image in the framebuffer
memory up to where the cursor is located. Add helpers to calculate
the offset and size.

Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
---
 drivers/gpu/drm/ast/ast_mode.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index c3b950675485..4cac5c7f4547 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -51,6 +51,24 @@
 
 #define AST_LUT_SIZE 256
 
+static unsigned long ast_fb_vram_offset(void)
+{
+       return 0; // with shmem, the primary plane is always at offset 0
+}
+
+static unsigned long ast_fb_vram_size(struct ast_device *ast)
+{
+       struct drm_device *dev = &ast->base;
+       unsigned long offset = ast_fb_vram_offset(); // starts at offset
+       long cursor_offset = ast_cursor_vram_offset(ast); // ends at cursor 
offset
+
+       if (cursor_offset < 0)
+               cursor_offset = ast->vram_size; // no cursor; it's all ours
+       if (drm_WARN_ON_ONCE(dev, offset > cursor_offset))
+               return 0; // cannot legally happen; signal error
+       return cursor_offset - offset;
+}
+
 static inline void ast_load_palette_index(struct ast_device *ast,
                                     u8 index, u8 red, u8 green,
                                     u8 blue)
@@ -609,9 +627,8 @@ static int ast_primary_plane_init(struct ast_device *ast)
        struct ast_plane *ast_primary_plane = &ast->primary_plane;
        struct drm_plane *primary_plane = &ast_primary_plane->base;
        void __iomem *vaddr = ast->vram;
-       u64 offset = 0; /* with shmem, the primary plane is always at offset 0 
*/
-       unsigned long cursor_size = roundup(AST_HWC_SIZE + 
AST_HWC_SIGNATURE_SIZE, PAGE_SIZE);
-       unsigned long size = ast->vram_fb_available - cursor_size;
+       u64 offset = ast_fb_vram_offset();
+       unsigned long size = ast_fb_vram_size(ast);
        int ret;
 
        ret = ast_plane_init(dev, ast_primary_plane, vaddr, offset, size,
@@ -942,7 +959,7 @@ static enum drm_mode_status 
ast_mode_config_mode_valid(struct drm_device *dev,
        struct ast_device *ast = to_ast_device(dev);
        unsigned long fbsize, fbpages, max_fbpages;
 
-       max_fbpages = (ast->vram_fb_available) >> PAGE_SHIFT;
+       max_fbpages = ast_fb_vram_size(ast) >> PAGE_SHIFT;
 
        fbsize = mode->hdisplay * mode->vdisplay * max_bpp;
        fbpages = DIV_ROUND_UP(fbsize, PAGE_SIZE);
-- 
2.48.1