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[Xen-devel] [PATCH v4 06/11] drivers/video/fbdev/arkfb.c: Use arch_phys_wc_add() and pci_iomap_wc()

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

Convert the driver from using the x86-specific MTRR code to the
architecture-agnostic arch_phys_wc_add(). It will avoid MTRRs if
write-combining is available. In order to take advantage of that also
ensure the ioremapped area is requested as write-combining.

There are a few motivations for this:

a) Take advantage of PAT when available.

b) Help bury MTRR code away, MTRR is architecture-specific and on
   x86 it is being replaced by PAT.

c) 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

The conversion done is expressed by the following Coccinelle
SmPL patch, it additionally required manual intervention to
address all the ifdeffery and removal of redundant things which
arch_phys_wc_add() already addresses such as verbose message about
when MTRR fails and doing nothing when we didn't get an MTRR.

@ mtrr_found @
expression index, base, size;

-index = mtrr_add(base, size, MTRR_TYPE_WRCOMB, 1);
+index = arch_phys_wc_add(base, size);

@ mtrr_rm depends on mtrr_found @
expression mtrr_found.index, mtrr_found.base, mtrr_found.size;

-mtrr_del(index, base, size);

@ mtrr_rm_zero_arg depends on mtrr_found @
expression mtrr_found.index;

-mtrr_del(index, 0, 0);

@ mtrr_rm_fb_info depends on mtrr_found @
struct fb_info *info;
expression mtrr_found.index;

-mtrr_del(index, info->fix.smem_start, info->fix.smem_len);

@ ioremap_replace_nocache depends on mtrr_found @
struct fb_info *info;
expression base, size;

-info->screen_base = ioremap_nocache(base, size);
+info->screen_base = ioremap_wc(base, size);

@ ioremap_replace_default depends on mtrr_found @
struct fb_info *info;
expression base, size;

-info->screen_base = ioremap(base, size);
+info->screen_base = ioremap_wc(base, size);

Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Acked-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Antonino Daplas <adaplas@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: benh@xxxxxxxxxxxxxxxxxxx
Cc: bhelgaas@xxxxxxxxxx
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: "Lad, Prabhakar" <prabhakar.csengg@xxxxxxxxx>
Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: linux-fbdev@xxxxxxxxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: mst@xxxxxxxxxx
Cc: Suresh Siddha <sbsiddha@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: toshi.kani@xxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
 drivers/video/fbdev/arkfb.c | 36 +++++-------------------------------
 1 file changed, 5 insertions(+), 31 deletions(-)

diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c
index b305a1e7cc76..6a317de7082c 100644
--- a/drivers/video/fbdev/arkfb.c
+++ b/drivers/video/fbdev/arkfb.c
@@ -26,13 +26,9 @@
 #include <linux/console.h> /* Why should fb driver call console functions? 
because console_lock() */
 #include <video/vga.h>
-#include <asm/mtrr.h>
 struct arkfb_info {
        int mclk_freq;
-       int mtrr_reg;
+       int wc_cookie;
        struct dac_info *dac;
        struct vgastate state;
@@ -102,10 +98,6 @@ static const struct svga_timing_regs ark_timing_regs     = {
 static char *mode_option = "640x480-8@60";
-static int mtrr = 1;
 MODULE_AUTHOR("(c) 2007 Ondrej Zajicek <santiago@xxxxxxxxxxxxx>");
 MODULE_DESCRIPTION("fbdev driver for ARK 2000PV");
@@ -115,11 +107,6 @@ MODULE_PARM_DESC(mode_option, "Default video mode 
('640x480-8@60', etc)");
 module_param_named(mode, mode_option, charp, 0444);
 MODULE_PARM_DESC(mode, "Default video mode ('640x480-8@60', etc) 
-module_param(mtrr, int, 0444);
-MODULE_PARM_DESC(mtrr, "Enable write-combining with MTRR (1=enable, 0=disable, 
 static int threshold = 4;
 module_param(threshold, int, 0644);
@@ -1002,7 +989,7 @@ static int ark_pci_probe(struct pci_dev *dev, const struct 
pci_device_id *id)
        info->fix.smem_len = pci_resource_len(dev, 0);
        /* Map physical IO memory address into kernel space */
-       info->screen_base = pci_iomap(dev, 0, 0);
+       info->screen_base = pci_iomap_wc(dev, 0, 0);
        if (! info->screen_base) {
                rc = -ENOMEM;
                dev_err(info->device, "iomap for framebuffer failed\n");
@@ -1057,14 +1044,8 @@ static int ark_pci_probe(struct pci_dev *dev, const 
struct pci_device_id *id)
        /* Record a reference to the driver data */
        pci_set_drvdata(dev, info);
-       if (mtrr) {
-               par->mtrr_reg = -1;
-               par->mtrr_reg = mtrr_add(info->fix.smem_start, 
info->fix.smem_len, MTRR_TYPE_WRCOMB, 1);
-       }
+       par->wc_cookie = arch_phys_wc_add(info->fix.smem_start,
+                                         info->fix.smem_len);
        return 0;
        /* Error handling */
@@ -1092,14 +1073,7 @@ static void ark_pci_remove(struct pci_dev *dev)
        if (info) {
                struct arkfb_info *par = info->par;
-               if (par->mtrr_reg >= 0) {
-                       mtrr_del(par->mtrr_reg, 0, 0);
-                       par->mtrr_reg = -1;
-               }
+               arch_phys_wc_del(par->wc_cookie);

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