[Xen-devel] [PATCH v8 4/9] video: fbdev: gxt4500: use pci_ioremap_wc_bar() for framebuffer

["Luis R. Rodriguez" <mcgrof@xxxxxxxxxxxxxxxx>]

From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>

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
   pci_mmap_page_range()")

Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Suresh Siddha <sbsiddha@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Antonino Daplas <adaplas@xxxxxxxxx>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx>
Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Cc: linux-fbdev@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
---
 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;
-- 
2.3.2.209.gd67f9d5.dirty


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