[PATCH 6/9] drm/panfrost: Add "clean only safe" feature bit

[Alyssa Rosenzweig]

> > Add the HW_FEATURE_CLEAN_ONLY_SAFE bit based on kbase. When I actually
> > tried to port the logic from kbase, trivial jobs raised Data Invalid
> > Faults, so this may depend on other coherency details. It's still useful
> > to have the bit to record the feature bit when adding new models.
> > 
> > Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
> 
> Reviewed-by: Steven Price <steven.price at arm.com>
> 
> Sadly I don't have the hardware to try this out on, but it should be a
> simple case of the below (untested):
> 
> ----8<----
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index 908d79520853..602e51c4966e 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -212,9 +212,13 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
>          * start */
>         cfg |= JS_CONFIG_THREAD_PRI(8) |
>                 JS_CONFIG_START_FLUSH_CLEAN_INVALIDATE |
> -               JS_CONFIG_END_FLUSH_CLEAN_INVALIDATE |
>                 panfrost_get_job_chain_flag(job);
>  
> +       if (panfrost_has_hw_feature(pfdev, HW_FEATURE_CLEAN_ONLY_SAFE))
> +               cfg |= JS_CONFIG_END_FLUSH_CLEAN;
> +       else
> +               cfg |= JS_CONFIG_END_FLUSH_CLEAN_INVALIDATE;
> +
>         if (panfrost_has_hw_feature(pfdev, HW_FEATURE_FLUSH_REDUCTION))
>                 cfg |= JS_CONFIG_ENABLE_FLUSH_REDUCTION;

Yes, this is the patch I typed out... causes DATA_INVALID_FAULTs for me
with Mesa. Which makes me wonder if userspace needs to respect some
extra rules for this to be safe.