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

[Jocelyn Falempe]

On 05/03/2025 17:30, Thomas Zimmermann wrote:
> 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.
> 
Thanks, it looks good to me.

Reviewed-by: Jocelyn Falempe <jfalempe at redhat.com>

> Signed-off-by: Thomas Zimmermann <tzimmermann at 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);