linux-kernel - [PATCH v2 1/3] drm/gem: don't force writecombine mmap'ing

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Date:   Tue, 16 Jul 2019 10:43:21 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Chris Wilson <chris@...is-wilson.co.uk>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Rob Clark <robdclark@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] drm/gem: don't force writecombine mmap'ing

From: Rob Clark <robdclark@...omium.org>

The driver should be in control of this.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
It is possible that this was masking bugs (ie. not setting appropriate
pgprot) in drivers.  I don't have a particularly good idea for tracking
those down (since I don't have the hw for most drivers).  Unless someone
has a better idea, maybe land this and let driver maintainers fix any
potential fallout in their drivers?

This is necessary for the last patch to fix VGEM brokenness on arm.

 drivers/gpu/drm/drm_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 8a55f71325b1..7d6242cc69f2 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1110,7 +1110,7 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 
 	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_private_data = obj;
-	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
 
 	/* Take a ref for this mapping of the object, so that the fault
-- 
2.21.0