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[Xen-devel] [PATCH v4 02/11] drivers/video/fbdev/i740fb: Use arch_phys_wc_add() and pci_ioremap_wc_bar()

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 MTRR 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: Benoit Taine <benoit.taine@xxxxxxx>
Cc: Bjorn Helgaas <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: Jingoo Han <jg1.han@xxxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: linux-fbdev@xxxxxxxxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: mst@xxxxxxxxxx
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Suresh Siddha <sbsiddha@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: toshi.kani@xxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
 drivers/video/fbdev/i740fb.c | 35 ++++++-----------------------------
 1 file changed, 6 insertions(+), 29 deletions(-)

diff --git a/drivers/video/fbdev/i740fb.c b/drivers/video/fbdev/i740fb.c
index a2b4204b42bb..452e1163ad02 100644
--- a/drivers/video/fbdev/i740fb.c
+++ b/drivers/video/fbdev/i740fb.c
@@ -27,24 +27,15 @@
 #include <linux/console.h>
 #include <video/vga.h>
-#include <asm/mtrr.h>
 #include "i740_reg.h"
 static char *mode_option;
 static int mtrr = 1;
 struct i740fb_par {
        unsigned char __iomem *regs;
        bool has_sgram;
-       int mtrr_reg;
+       int wc_cookie;
        bool ddc_registered;
        struct i2c_adapter ddc_adapter;
        struct i2c_algo_bit_data ddc_algo;
@@ -1040,7 +1031,7 @@ static int i740fb_probe(struct pci_dev *dev, const struct 
pci_device_id *ent)
                goto err_request_regions;
-       info->screen_base = pci_ioremap_bar(dev, 0);
+       info->screen_base = pci_ioremap_wc_bar(dev, 0);
        if (!info->screen_base) {
                dev_err(info->device, "error remapping base\n");
                ret = -ENOMEM;
@@ -1144,13 +1135,9 @@ static int i740fb_probe(struct pci_dev *dev, const 
struct pci_device_id *ent)
        fb_info(info, "%s frame buffer device\n", info->fix.id);
        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);
-       }
+       if (mtrr)
+               par->wc_cookie = arch_phys_wc_add(info->fix.smem_start,
+                                                 info->fix.smem_len);
        return 0;
@@ -1177,13 +1164,7 @@ static void i740fb_remove(struct pci_dev *dev)
        if (info) {
                struct i740fb_par *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);
                if (par->ddc_registered)
@@ -1287,10 +1268,8 @@ static int  __init i740fb_setup(char *options)
        while ((opt = strsep(&options, ",")) != NULL) {
                if (!*opt)
                else if (!strncmp(opt, "mtrr:", 5))
                        mtrr = simple_strtoul(opt + 5, NULL, 0);
                        mode_option = opt;
@@ -1327,7 +1306,5 @@ MODULE_DESCRIPTION("fbdev driver for Intel740");
 module_param(mode_option, charp, 0444);
 MODULE_PARM_DESC(mode_option, "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, 

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