[Mesa-dev] [PATCH] i965/skl: Don't use the PMA depth stall workaround

[Anuj Phogat]

On Wed, Mar 25, 2015 at 4:52 PM, Ben Widawsky
<benjamin.widawsky at intel.com> wrote:
> The PMA depth stall must be enabled (optimization turned off) under certain
> circumstances on gen8. This was supposedly fixed for Gen9, which means we do not
> need to check, or toggle the state. The hardware is supposed to enable the
> hardware optimization by default, unlike BDW, so we also don't need to set it at
> init. For whatever reason this improves stability on ETQW with the bug mentioned
> below.
>
> TODO: This patch still needs to be tested on a full piglit run.
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=89039 (doesn't fix)
> Cc: Anuj Phogat <anuj.phogat at intel.com>
> Cc: Eero Tamminen <eero.t.tamminen at intel.com>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
>  src/mesa/drivers/dri/i965/gen8_depth_state.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/gen8_depth_state.c b/src/mesa/drivers/dri/i965/gen8_depth_state.c
> index c6494c9..3d126cf 100644
> --- a/src/mesa/drivers/dri/i965/gen8_depth_state.c
> +++ b/src/mesa/drivers/dri/i965/gen8_depth_state.c
> @@ -368,6 +368,10 @@ static void
>  gen8_emit_pma_stall_workaround(struct brw_context *brw)
>  {
>     uint32_t bits = 0;
> +
> +   if (brw->gen >= 9)
> +      return;
> +
>     if (pma_fix_enable(brw))
>        bits |= GEN8_HIZ_NP_PMA_FIX_ENABLE | GEN8_HIZ_NP_EARLY_Z_FAILS_DISABLE;
>
> @@ -400,7 +404,8 @@ gen8_hiz_exec(struct brw_context *brw, struct intel_mipmap_tree *mt,
>        return;
>
>     /* Disable the PMA stall fix since we're about to do a HiZ operation. */
> -   write_pma_stall_bits(brw, 0);
> +   if (brw->gen == 8)
> +      write_pma_stall_bits(brw, 0);
>
>     assert(mt->first_level == 0);
>     assert(mt->logical_depth0 >= 1);
> --
> 2.3.3
>
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Tested the patch with ETQW demo.

Tested-by: Anuj Phogat <anuj.phogat at gmail.com>