FAILED: patch "[PATCH] drm/i915/gt: Program mocs:63 for cache eviction on gen9" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 777a7717d60ccdc9b84f35074f848d3f746fc3bf Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Thu, 26 Nov 2020 14:08:41 +0000
Subject: [PATCH] drm/i915/gt: Program mocs:63 for cache eviction on gen9
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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

index 313e51e7d4f7..4f74706967fd 100644
@@ -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 */