ongoing writecombine on ppc

From: Dave Airlie <airlied@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Jerome Glisse <j.glisse@gmail.com>,
	Oded Gabbay <oded.gabbay@gmail.com>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: ongoing writecombine on ppc
Date: Fri, 2 Oct 2015 14:42:53 +1000	[thread overview]
Message-ID: <CAPM=9twpPBLBb6j1ee5_DDv5UqfTzCJh-63CHyDxRU4Xd0ny4g@mail.gmail.com> (raw)

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I don't think we resolved this the last time we talked about it,

but radeon writecombine maps fail hard on ppc, I think all the fixes
either did something bad to AGP systems or weren't liked.

My patch attached just fixes radeon, which is where I'm still seeing the issue.

Dave.

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From 67d00d2fcb756a3d2b6061d0831242138889a81f Mon Sep 17 00:00:00 2001
From: Dave Airlie <airlied@redhat.com>
Date: Fri, 2 Oct 2015 12:22:08 +1000
Subject: [PATCH] radeon: don't attempt WC mappings on powerpc

---
 drivers/gpu/drm/radeon/radeon_object.c | 16 ++++++++++++----
 include/drm/drm_cache.h                |  9 +++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index d302488..4acda0e 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <drm/drmP.h>
 #include <drm/radeon_drm.h>
+#include <drm/drm_cache.h>
 #include "radeon.h"
 #include "radeon_trace.h"
 
@@ -92,6 +93,15 @@ bool radeon_ttm_bo_is_radeon_bo(struct ttm_buffer_object *bo)
 	return false;
 }
 
+static inline bool radeon_placement_can_wc(struct radeon_bo *rbo)
+{
+	if ((rbo->flags & RADEON_GEM_GTT_WC) && drm_arch_can_wc_memory())
+		return true;
+	if (rbo->rdev->flags & RADEON_IS_AGP)
+		return true;
+	return false;
+}
+
 void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
 {
 	u32 c = 0, i;
@@ -123,8 +133,7 @@ void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
 			rbo->placements[c++].flags = TTM_PL_FLAG_UNCACHED |
 				TTM_PL_FLAG_TT;
 
-		} else if ((rbo->flags & RADEON_GEM_GTT_WC) ||
-			   (rbo->rdev->flags & RADEON_IS_AGP)) {
+		} else if (radeon_placement_can_wc(rbo)) {
 			rbo->placements[c].fpfn = 0;
 			rbo->placements[c++].flags = TTM_PL_FLAG_WC |
 				TTM_PL_FLAG_UNCACHED |
@@ -142,8 +151,7 @@ void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
 			rbo->placements[c++].flags = TTM_PL_FLAG_UNCACHED |
 				TTM_PL_FLAG_SYSTEM;
 
-		} else if ((rbo->flags & RADEON_GEM_GTT_WC) ||
-		    rbo->rdev->flags & RADEON_IS_AGP) {
+		} else if (radeon_placement_can_wc(rbo)) {
 			rbo->placements[c].fpfn = 0;
 			rbo->placements[c++].flags = TTM_PL_FLAG_WC |
 				TTM_PL_FLAG_UNCACHED |
diff --git a/include/drm/drm_cache.h b/include/drm/drm_cache.h
index 7bfb063..461a055 100644
--- a/include/drm/drm_cache.h
+++ b/include/drm/drm_cache.h
@@ -35,4 +35,13 @@
 
 void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
 
+static inline bool drm_arch_can_wc_memory(void)
+{
+#if defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE)
+	return false;
+#else
+	return true;
+#endif
+}
+
 #endif
-- 
2.4.3


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