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Subject[PATCH v3 4/4] video: fbdev: gxt4500: use pci_ioremap_wc_bar() for framebuffer
From: "Luis R. Rodriguez" <>

The driver doesn't use mtrr_add() or arch_phys_wc_add() but
since we know the framebuffer is isolated already on an
ioremap() we can take advantage of write combining for
performance where possible.

In this case there are a few motivations for this:

a) Take advantage of PAT when available

b) Help with the goal of eventually using _PAGE_CACHE_UC over
_PAGE_CACHE_UC_MINUS on x86 on ioremap_nocache() (see commit
de33c442e titled "x86 PAT: fix performance drop for glx,
use UC minus for ioremap(), ioremap_nocache() and

Cc: Laurent Pinchart <>
Cc: Rob Clark <>
Cc: Geert Uytterhoeven <>
Cc: Suresh Siddha <>
Cc: Ingo Molnar <>
Cc: Thomas Gleixner <>
Cc: Juergen Gross <>
Cc: Daniel Vetter <>
Cc: Andy Lutomirski <>
Cc: Dave Airlie <>
Cc: Antonino Daplas <>
Cc: Jean-Christophe Plagniol-Villard <>
Cc: Tomi Valkeinen <>
Signed-off-by: Luis R. Rodriguez <>
drivers/video/fbdev/gxt4500.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/gxt4500.c b/drivers/video/fbdev/gxt4500.c
index 135d78a..f19133a 100644
--- a/drivers/video/fbdev/gxt4500.c
+++ b/drivers/video/fbdev/gxt4500.c
@@ -662,7 +662,7 @@ static int gxt4500_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

info->fix.smem_start = fb_phys;
info->fix.smem_len = pci_resource_len(pdev, 1);
- info->screen_base = pci_ioremap_bar(pdev, 1);
+ info->screen_base = pci_ioremap_wc_bar(pdev, 1);
if (!info->screen_base) {
dev_err(&pdev->dev, "gxt4500: cannot map framebuffer\n");
goto err_unmap_regs;

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