From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Wed, 5 Mar 2025 16:30:44 +0000 (+0100)
Subject: drm/ast: Add helper for computing framebuffer location in video memory
X-Git-Tag: v6.16-rc1~144^2~21^2~216
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ca7a8e8efc9cba4f131b65197bae5011d0a7a250;p=thirdparty%2Flinux.git

drm/ast: Add helper for computing framebuffer location in video memory

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 <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250305163207.267650-6-tzimmermann@suse.de
---

diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index c3b9506754858..4cac5c7f45474 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);