linux-kernel - [PATCH v4 04/11] drivers/video/fbdev/gxt4500: Use pci_ioremap_wc

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Message-Id: <1440443613-13696-5-git-send-email-mcgrof@do-not-panic.com>
Date:	Mon, 24 Aug 2015 12:13:26 -0700
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	mingo@...nel.org
Cc:	bp@...e.de, bhelgaas@...gle.com, tomi.valkeinen@...com,
	airlied@...ux.ie, linux-fbdev@...r.kernel.org, luto@...capital.net,
	vinod.koul@...el.com, dan.j.williams@...el.com, toshi.kani@...com,
	benh@...nel.crashing.org, mst@...hat.com,
	akpm@...ux-foundation.org, daniel.vetter@...ll.ch,
	konrad.wilk@...cle.com, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	xen-devel@...ts.xensource.com,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Antonino Daplas <adaplas@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Dave Airlie <airlied@...hat.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Juergen Gross <jgross@...e.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Rob Clark <robdclark@...il.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v4 04/11] drivers/video/fbdev/gxt4500: Use pci_ioremap_wc_bar() to map 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() (see commit
   de33c442e titled "x86 PAT: fix performance drop for glx,
   use UC minus for ioremap(), ioremap_nocache() and
   pci_mmap_page_range()").

Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>
Acked-by: Tomi Valkeinen <tomi.valkeinen@...com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Antonino Daplas <adaplas@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: benh@...nel.crashing.org
Cc: bhelgaas@...gle.com
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Dave Airlie <airlied@...hat.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-fbdev@...r.kernel.org
Cc: linux-pci@...r.kernel.org
Cc: mst@...hat.com
Cc: Rob Clark <robdclark@...il.com>
Cc: Suresh Siddha <sbsiddha@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: toshi.kani@...com
Link: http://lkml.kernel.org/r/1435195342-26879-5-git-send-email-mcgrof@do-not-panic.com
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 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 135d78a02588..f19133a80e8c 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;
-- 
2.4.3

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