linux-kernel - [PATCH v3 16/17] video: fbdev: atmel_lcdfb: use ioremap

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Date:	Tue, 21 Apr 2015 13:16:37 -0700
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	plagnioj@...osoft.com, tomi.valkeinen@...com
Cc:	linux-fbdev@...r.kernel.org, luto@...capital.net,
	cocci@...teme.lip6.fr, "Luis R. Rodriguez" <mcgrof@...e.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juergen Gross <jgross@...e.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Dave Airlie <airlied@...hat.com>,
	Antonino Daplas <adaplas@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 16/17] video: fbdev: atmel_lcdfb: use ioremap_wc() 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() (see commit
   de33c442e titled "x86 PAT: fix performance drop for glx,
   use UC minus for ioremap(), ioremap_nocache() and
   pci_mmap_page_range()")

Cc: Nicolas Ferre <nicolas.ferre@...el.com>
Cc: Suresh Siddha <sbsiddha@...il.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/atmel_lcdfb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/atmel_lcdfb.c b/drivers/video/fbdev/atmel_lcdfb.c
index 94a8d04..abadc49 100644
--- a/drivers/video/fbdev/atmel_lcdfb.c
+++ b/drivers/video/fbdev/atmel_lcdfb.c
@@ -1266,7 +1266,8 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev)
 			goto stop_clk;
 		}
 
-		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) {
 			ret = -ENOMEM;
 			goto release_intmem;
-- 
2.3.2.209.gd67f9d5.dirty

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