Re: [PATCH v3] drm: mxsfb: check framebuffer pitch

[Stefan Agner]

On 2020-09-08 16:16, Stefan Agner wrote:
> The lcdif IP does not support a framebuffer pitch (stride) other than
> framebuffer width. Check for equality and reject the framebuffer
> otherwise.
> 
> This prevents a distorted picture when using 640x800 and running the
> Mesa graphics stack. Mesa tries to use a cache aligned stride, which
> leads at that particular resolution to width != stride. Currently
> Mesa has no fallback behavior, but rejecting this configuration allows
> userspace to handle the issue correctly.
> 
> Fixes: 45d59d704080 ("drm: Add new driver for MXSFB controller")
> Signed-off-by: Stefan Agner 
> Reviewed-by: Laurent Pinchart 

Applied to drm-misc-next.

--
Stefan

> ---
> Changes in v3:
> - Fix typo in commit message
> - Add fixes tag
> 
> Changes in v2:
> - Validate pitch in fb_create callback
> 
>  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 21 -
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index 8c549c3931af..35122aef037b 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -21,6 +21,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -81,8 +82,26 @@ void mxsfb_disable_axi_clk(struct mxsfb_drm_private *mxsfb)
>   clk_disable_unprepare(mxsfb->clk_axi);
>  }
>  
> +static struct drm_framebuffer *
> +mxsfb_fb_create(struct drm_device *dev, struct drm_file *file_priv,
> + const struct drm_mode_fb_cmd2 *mode_cmd)
> +{
> + const struct drm_format_info *info;
> +
> + info = drm_get_format_info(dev, mode_cmd);
> + if (!info)
> + return ERR_PTR(-EINVAL);
> +
> + if (mode_cmd->width * info->cpp[0] != mode_cmd->pitches[0]) {
> + dev_dbg(dev->dev, "Invalid pitch: fb width must match pitch\n");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + return drm_gem_fb_create(dev, file_priv, mode_cmd);
> +}
> +
>  static const struct drm_mode_config_funcs mxsfb_mode_config_funcs = {
> - .fb_create  = drm_gem_fb_create,
> + .fb_create  = mxsfb_fb_create,
>   .atomic_check   = drm_atomic_helper_check,
>   .atomic_commit  = drm_atomic_helper_commit,
>  };

[PATCH v3] drm: mxsfb: check framebuffer pitch

[Stefan Agner]

The lcdif IP does not support a framebuffer pitch (stride) other than
framebuffer width. Check for equality and reject the framebuffer
otherwise.

This prevents a distorted picture when using 640x800 and running the
Mesa graphics stack. Mesa tries to use a cache aligned stride, which
leads at that particular resolution to width != stride. Currently
Mesa has no fallback behavior, but rejecting this configuration allows
userspace to handle the issue correctly.

Fixes: 45d59d704080 ("drm: Add new driver for MXSFB controller")
Signed-off-by: Stefan Agner 
Reviewed-by: Laurent Pinchart 
---
Changes in v3:
- Fix typo in commit message
- Add fixes tag

Changes in v2:
- Validate pitch in fb_create callback

 drivers/gpu/drm/mxsfb/mxsfb_drv.c | 21 -
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c 
b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
index 8c549c3931af..35122aef037b 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
@@ -21,6 +21,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -81,8 +82,26 @@ void mxsfb_disable_axi_clk(struct mxsfb_drm_private *mxsfb)
clk_disable_unprepare(mxsfb->clk_axi);
 }
 
+static struct drm_framebuffer *
+mxsfb_fb_create(struct drm_device *dev, struct drm_file *file_priv,
+   const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+   const struct drm_format_info *info;
+
+   info = drm_get_format_info(dev, mode_cmd);
+   if (!info)
+   return ERR_PTR(-EINVAL);
+
+   if (mode_cmd->width * info->cpp[0] != mode_cmd->pitches[0]) {
+   dev_dbg(dev->dev, "Invalid pitch: fb width must match pitch\n");
+   return ERR_PTR(-EINVAL);
+   }
+
+   return drm_gem_fb_create(dev, file_priv, mode_cmd);
+}
+
 static const struct drm_mode_config_funcs mxsfb_mode_config_funcs = {
-   .fb_create  = drm_gem_fb_create,
+   .fb_create  = mxsfb_fb_create,
.atomic_check   = drm_atomic_helper_check,
.atomic_commit  = drm_atomic_helper_commit,
 };
-- 
2.28.0