Hi Ville,
On 10/13/2023 12:50 PM, Ville Syrjälä wrote:
On Fri, Oct 13, 2023 at 12:31:40PM +0200, Nirmoy Das wrote:
gen8_ggtt_invalidate() is only needed for limitted set of platforms
where GGTT is mapped as WC
I know there is supposed to be some kind hw snooping of the ggtt
pte writes to invalidate the tlb, but are we sure GFX_FLSH_CNTL
has no other side effects we depend on?
I spent some time searching through the gfxspec. This GFX_FLSH_CNTL
register only seems to be for
invalidating TLB for GUnit and (from git log ) we started to do that to
enable WC based GGTT updates.
So if I am not missing anything obvious then this should be safe.
Regards,
Nirmoy
otherwise this can cause unwanted
side-effects on XE_HP platforms where GFX_FLSH_CNTL_GEN6 is not
valid.
Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
Cc: John Harrison <john.c.harrison@xxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.2+
Suggested-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_ggtt.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 4d7d88b92632..c2858d434bce 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -197,13 +197,17 @@ void gen6_ggtt_invalidate(struct i915_ggtt *ggtt)
static void gen8_ggtt_invalidate(struct i915_ggtt *ggtt)
{
+ struct drm_i915_private *i915 = ggtt->vm.i915;
struct intel_uncore *uncore = ggtt->vm.gt->uncore;
/*
* Note that as an uncached mmio write, this will flush the
* WCB of the writes into the GGTT before it triggers the invalidate.
+ *
+ * Only perform this when GGTT is mapped as WC, see ggtt_probe_common().
*/
- intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
+ if (!IS_GEN9_LP(i915) && GRAPHICS_VER(i915) < 11)
+ intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
}
static void guc_ggtt_invalidate(struct i915_ggtt *ggtt)
--
2.41.0
