[Intel-gfx] [PATCH] drm/i915/gt: Disable HiZ Raw Stall Optimization on broken gen7

[Dave Airlie]

Reviewed-by: Dave Airlie <airlied at redhat.com>

Can we get this fix in, having a regression spanning 3 kernels isn't a
good look, we can work out why it matters later in life if anyone
cares.

Dave.

On Tue, 27 Apr 2021 at 00:31, Simon Rettberg
<simon.rettberg at rz.uni-freiburg.de> wrote:
>
> When resetting CACHE_MODE registers, don't enable HiZ Raw Stall
> Optimization on Ivybridge GT1 and Baytrail, as it causes severe glitches
> when rendering any kind of 3D accelerated content.
> This optimization is disabled on these platforms by default according to
> official documentation from 01.org.
>
> Fixes: ef99a60ffd9b ("drm/i915/gt: Clear CACHE_MODE prior to clearing residuals")
> Fixes: 520d05a77b28 ("drm/i915/gt: Clear CACHE_MODE prior to clearing residuals")
> BugLink: https://gitlab.freedesktop.org/drm/intel/-/issues/3081
> BugLink: https://gitlab.freedesktop.org/drm/intel/-/issues/3404
> BugLink: https://gitlab.freedesktop.org/drm/intel/-/issues/3071
> Reviewed-By: Manuel Bentele <development at manuel-bentele.de>
> Signed-off-by: Simon Rettberg <simon.rettberg at rz.uni-freiburg.de>
> ---
>  drivers/gpu/drm/i915/gt/gen7_renderclear.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/gen7_renderclear.c b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> index de575fdb0..21f08e538 100644
> --- a/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> +++ b/drivers/gpu/drm/i915/gt/gen7_renderclear.c
> @@ -397,7 +397,10 @@ static void emit_batch(struct i915_vma * const vma,
>         gen7_emit_pipeline_invalidate(&cmds);
>         batch_add(&cmds, MI_LOAD_REGISTER_IMM(2));
>         batch_add(&cmds, i915_mmio_reg_offset(CACHE_MODE_0_GEN7));
> -       batch_add(&cmds, 0xffff0000);
> +       batch_add(&cmds, 0xffff0000 |
> +                       ((IS_IVB_GT1(i915) || IS_VALLEYVIEW(i915)) ?
> +                        HIZ_RAW_STALL_OPT_DISABLE :
> +                        0));
>         batch_add(&cmds, i915_mmio_reg_offset(CACHE_MODE_1));
>         batch_add(&cmds, 0xffff0000 | PIXEL_SUBSPAN_COLLECT_OPT_DISABLE);
>         gen7_emit_pipeline_invalidate(&cmds);
> --
> 2.25.1
>
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