On 11/02/2022 20:27, alyssa.rosenzweig@xxxxxxxxxxxxx wrote:
> From: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx>
>
> TTRX_3485 requires the infamous "dummy job" workaround. I have this
> workaround implemented in a local branch, but I have not yet hit a case
> that requires it so I cannot test whether the implementation is correct.
> In the mean time, add the quirk bit so we can document which platforms
> may need it in the future.
This one is hideous ;) Although to me this isn't the 'infamous' one as
it's not the earliest example of a dummy job.
However... I believe as Panfrost currently stands this is probably not
very possible to hit. It requires a job to be stopped (soft or hard) at
a critical point during submission - which at the moment Panfrost
basically never does (the exception is if you close the fd immediately
while a job is in progress). And of course the timing has to be 'just
right' to hit the bug.
That said I think we should probably add pre-emption support sometime at
which point this could become an issue.
> Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
> ---
> drivers/gpu/drm/panfrost/panfrost_issues.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_issues.h b/drivers/gpu/drm/panfrost/panfrost_issues.h
> index 058f6a4c8435..b8865fc9efce 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_issues.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_issues.h
> @@ -132,6 +132,9 @@ enum panfrost_hw_issue {
> * to hang */
> HW_ISSUE_TTRX_3076,
>
> + /* Must issue a dummy job before starting real work to prevent hangs */
> + HW_ISSUE_TTRX_3485,
> +
> HW_ISSUE_END
> };
>
