From b640cd15eb66164788b7db96f422c724245b4984 Mon Sep 17 00:00:00 2001
From: Matthew Auld <matthew.auld@intel.com>
Date: Fri, 3 Sep 2021 16:53:17 +0100
Subject: drm/i915/gtt: add some flushing for the 64K GTT path
Git-commit: 502d0609fc418e674f1e8bd30aa02748e4c6b465
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

If we need to mark the PDE as operating in 64K GTT mode, we should be
paranoid and flush the extra writes, like we already do for the PTEs. On
some platforms the clflush can apparently add the just the right amount
of magical delay to force the GPU to see the updated entry.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210903155317.1854012-1-matthew.auld@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
index 6e0e52eeb87a..6a5af995f5b1 100644
--- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
@@ -548,6 +548,7 @@ static void gen8_ppgtt_insert_huge(struct i915_vma *vma,
 					      I915_GTT_PAGE_SIZE_2M)))) {
 			vaddr = px_vaddr(pd);
 			vaddr[maybe_64K] |= GEN8_PDE_IPS_64K;
+			clflush_cache_range(vaddr, PAGE_SIZE);
 			page_size = I915_GTT_PAGE_SIZE_64K;
 
 			/*
@@ -568,6 +569,7 @@ static void gen8_ppgtt_insert_huge(struct i915_vma *vma,
 				for (i = 1; i < index; i += 16)
 					memset64(vaddr + i, encode, 15);
 
+				clflush_cache_range(vaddr, PAGE_SIZE);
 			}
 		}
 
-- 
2.38.1