gen8_ggtt_invalidate() is only needed for limited set of platforms
where GGTT is mapped as WC. This was added as way to fix WC based GGTT in
commit 0f9b91c754b7 ("drm/i915: flush system agent TLBs on SNB") and
there are no reference in HW docs that forces us to use this on non-WC
backed GGTT.
This can also cause unwanted side-effects on XE_HP platforms where
GFX_FLSH_CNTL_GEN6 is not valid anymore.
v2: Add a func to detect wc ggtt detection (Ville)
v3: Improve commit log and add reference commit (Daniel)
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: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.2+
Suggested-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_ggtt.c | 35 +++++++++++++++++++---------
1 file changed, 24 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 1c93e84278a0..15fc8e4703f4 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -195,6 +195,21 @@ void gen6_ggtt_invalidate(struct i915_ggtt *ggtt)
spin_unlock_irq(&uncore->lock);
}
+static bool needs_wc_ggtt_mapping(struct drm_i915_private *i915)
+{
+ /*
+ * On BXT+/ICL+ writes larger than 64 bit to the GTT pagetable range
+ * will be dropped. For WC mappings in general we have 64 byte burst
+ * writes when the WC buffer is flushed, so we can't use it, but have to
+ * resort to an uncached mapping. The WC issue is easily caught by the
+ * readback check when writing GTT PTE entries.
+ */
+ if (!IS_GEN9_LP(i915) && GRAPHICS_VER(i915) < 11)
+ return true;
+
+ return false;
+}
+
static void gen8_ggtt_invalidate(struct i915_ggtt *ggtt)
{
struct intel_uncore *uncore = ggtt->vm.gt->uncore;
@@ -202,8 +217,12 @@ static void gen8_ggtt_invalidate(struct i915_ggtt *ggtt)
/*
* 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 (needs_wc_ggtt_mapping(ggtt->vm.i915))
+ intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6,
+ GFX_FLSH_CNTL_EN);
}
static void guc_ggtt_ct_invalidate(struct intel_gt *gt)
@@ -1140,17 +1159,11 @@ static int ggtt_probe_common(struct i915_ggtt *ggtt, u64 size)
GEM_WARN_ON(pci_resource_len(pdev, GEN4_GTTMMADR_BAR) != gen6_gttmmadr_size(i915));
phys_addr = pci_resource_start(pdev, GEN4_GTTMMADR_BAR) + gen6_gttadr_offset(i915);
- /*
- * On BXT+/ICL+ writes larger than 64 bit to the GTT pagetable range
- * will be dropped. For WC mappings in general we have 64 byte burst
- * writes when the WC buffer is flushed, so we can't use it, but have to
- * resort to an uncached mapping. The WC issue is easily caught by the
- * readback check when writing GTT PTE entries.
- */
- if (IS_GEN9_LP(i915) || GRAPHICS_VER(i915) >= 11)
- ggtt->gsm = ioremap(phys_addr, size);
- else
+ if (needs_wc_ggtt_mapping(i915))
ggtt->gsm = ioremap_wc(phys_addr, size);
+ else
+ ggtt->gsm = ioremap(phys_addr, size);
+
if (!ggtt->gsm) {
drm_err(&i915->drm, "Failed to map the ggtt page table\n");
return -ENOMEM;
--
2.41.0
