linux-kernel - [PATCH v1 46/47] video: fbdev: gxt4500: use pci_ioremap_wc

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Date:	Fri, 20 Mar 2015 16:18:36 -0700
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	luto@...capital.net, mingo@...hat.com, tglx@...utronix.de,
	hpa@...or.com, jgross@...e.com, JBeulich@...e.com, bp@...e.de,
	suresh.b.siddha@...el.com, venkatesh.pallipadi@...el.com,
	airlied@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
	x86@...nel.org, xen-devel@...ts.xenproject.org,
	"Luis R. Rodriguez" <mcgrof@...e.com>, Ingo Molnar <mingo@...e.hu>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Antonino Daplas <adaplas@...il.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>
Subject: [PATCH v1 46/47] video: fbdev: gxt4500: use pci_ioremap_wc_bar() for framebuffer

From: "Luis R. Rodriguez" <mcgrof@...e.com>

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() (de33c442e)

Cc: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Juergen Gross <jgross@...e.com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Dave Airlie <airlied@...hat.com>
Cc: Antonino Daplas <adaplas@...il.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@...com>
Cc: linux-fbdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>
---
 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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