[Mesa-dev] [PATCH] i965: Disable guardband clipping on SandyBridge for odd dimensions

[Matt Turner]

On Thu, May 24, 2018 at 4:16 AM, vadym.shovkoplias
<vadim.shovkoplias at gmail.com> wrote:
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104388
> Signed-off-by: Andriy Khulap <andriy.khulap at globallogic.com>
> ---
>  src/mesa/drivers/dri/i965/genX_state_upload.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c b/src/mesa/drivers/dri/i965/genX_state_upload.c
> index b485e2c..5aa8033 100644
> --- a/src/mesa/drivers/dri/i965/genX_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
> @@ -2473,6 +2473,17 @@ brw_calculate_guardband_size(uint32_t fb_width, uint32_t fb_height,
>      */
>     const float gb_size = GEN_GEN >= 7 ? 16384.0f : 8192.0f;
>
> +   /* Workaround: prevent gpu hangs on SandyBridge
> +    * by disabling guardband clipping for odd dimensions.
> +    */
> +   if (GEN_GEN == 6 && (fb_width & 1 || fb_height & 1)) {
> +      *xmin = -1.0f;
> +      *xmax =  1.0f;
> +      *ymin = -1.0f;
> +      *ymax =  1.0f;
> +      return;
> +   }

What's the theory? That odd dimension guard band is buggy on
Sandybridge? Do we have any documentation to support that theory?