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Subject[PATCH v3 17/17] video: fbdev: geode gxfb: use ioremap_wc() 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: Sudip Mukherjee <>
Cc: Geert Uytterhoeven <>
Cc: Laurent Pinchart <>
Cc: Jingoo Han <>
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/geode/gxfb_core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/geode/gxfb_core.c b/drivers/video/fbdev/geode/gxfb_core.c
index 124d7c7..ec9fc9a 100644
--- a/drivers/video/fbdev/geode/gxfb_core.c
+++ b/drivers/video/fbdev/geode/gxfb_core.c
@@ -263,7 +263,8 @@ static int gxfb_map_video_memory(struct fb_info *info, struct pci_dev *dev)

info->fix.smem_start = pci_resource_start(dev, 0);
info->fix.smem_len = vram ? vram : gx_frame_buffer_size();
- info->screen_base = ioremap(info->fix.smem_start, info->fix.smem_len);
+ info->screen_base = ioremap_wc(info->fix.smem_start,
+ info->fix.smem_len);
if (!info->screen_base)
return -ENOMEM;


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