From 777a7717d60ccdc9b84f35074f848d3f746fc3bf Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 26 Nov 2020 14:08:41 +0000
Subject: [PATCH] drm/i915/gt: Program mocs:63 for cache eviction on gen9
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Git-commit: 777a7717d60ccdc9b84f35074f848d3f746fc3bf
Patch-mainline: v5.10-rc7
No-fix: 977933b5da7c16f39295c4c1d4259a58ece65dbe
References: git-fixes
Ville noticed that the last mocs entry is used unconditionally by the HW
when it performs cache evictions, and noted that while the value is not
meant to be writable by the driver, we should program it to a reasonable
value nevertheless.
As it turns out, we can change the value of mocs:63 and the value we
were programming into it would cause hard hangs in conjunction with
atomic operations.
V2: Add details from bspec about how it is used by HW
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2707
Fixes: 3bbaba0ceaa2 ("drm/i915: Added Programming of the MOCS")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: <stable@vger.kernel.org> # v4.3+
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201126140841.1982-1-chris@chris-wilson.co.uk
(cherry picked from commit 977933b5da7c16f39295c4c1d4259a58ece65dbe)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/gt/intel_mocs.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
index 313e51e7d4f7..4f74706967fd 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -131,7 +131,19 @@ static const struct drm_i915_mocs_entry skl_mocs_table[] = {
GEN9_MOCS_ENTRIES,
MOCS_ENTRY(I915_MOCS_CACHED,
LE_3_WB | LE_TC_2_LLC_ELLC | LE_LRUM(3),
- L3_3_WB)
+ L3_3_WB),
+
+ /*
+ * mocs:63
+ * - used by the L3 for all of its evictions.
+ * Thus it is expected to allow LLC cacheability to enable coherent
+ * flows to be maintained.
+ * - used to force L3 uncachable cycles.
+ * Thus it is expected to make the surface L3 uncacheable.
+ */
+ MOCS_ENTRY(63,
+ LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+ L3_1_UC)
};
/* NOTE: the LE_TGT_CACHE is not used on Broxton */
--
2.26.2