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List:       linux-ia64
Subject:    Re: pgprot_writecombine & shub 1.x
From:       Jesse Barnes <jbarnes () sgi ! com>
Date:       2005-01-19 22:53:00
Message-ID: 200501191453.00489.jbarnes () sgi ! com
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On Wednesday, January 19, 2005 2:39 pm, David Mosberger wrote:
>   Jesse> Sounds good, though that could be a long wait.  Should we add
>   Jesse> this new EFI call anyway?  Seems like it'll be useful
>   Jesse> regardless...
>
> I agree.

Ok, here you go Tony.  This one fixes the loop and also fixes drm_vm.c.  All 
of the bits aside from the efi.h bit are ia64 specific (either under 
arch/ia64 or __ia64__), so your tree is probably the right place for all of 
it.

This patch adds efi_range_is_wc() to efi.h.  It's used to determine whether an 
address range can be mapped with the write coalescing attribute.  It also 
fixes up some ia64 specific callers to use the new routine instead of 
unconditionally calling pgprot_writecombined, which can be dangerous if used 
on ranges that don't support it.

Signed-off-by: Jesse Barnes <jbarnes@sgi.com>

Thanks,
Jesse

["efi-check-wc-range-6.patch" (text/plain)]

===== arch/ia64/pci/pci.c 1.65 vs edited =====
--- 1.65/arch/ia64/pci/pci.c	2005-01-12 10:08:48 -08:00
+++ edited/arch/ia64/pci/pci.c	2005-01-19 11:09:32 -08:00
@@ -539,7 +539,8 @@
 	 */
 	vma->vm_flags |= (VM_SHM | VM_RESERVED | VM_IO);
 
-	if (write_combine)
+	if (write_combine && efi_range_is_wc(vma->vm_start,
+					     vma->vm_end - vma->vm_start))
 		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 	else
 		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
===== drivers/char/drm/drm_vm.c 1.36 vs edited =====
--- 1.36/drivers/char/drm/drm_vm.c	2004-11-04 02:35:43 -08:00
+++ edited/drivers/char/drm/drm_vm.c	2005-01-19 14:31:47 -08:00
@@ -612,8 +612,13 @@
 			vma->vm_flags |= VM_IO;	/* not in core dump */
 		}
 #if defined(__ia64__)
-		if (map->type != _DRM_AGP)
-			vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+		if (efi_range_is_wc(vma->vm_start, vma->vm_end -
+				    vma->vm_start))
+			vma->vm_page_prot =
+				pgprot_writecombine(vma->vm_page_prot);
+		else
+			vma->vm_page_prot =
+				pgprot_noncached(vma->vm_page_prot);
 #endif
 		offset = dev->driver->get_reg_ofs(dev);
 #ifdef __sparc__
===== drivers/video/fbmem.c 1.148 vs edited =====
--- 1.148/drivers/video/fbmem.c	2005-01-05 15:46:41 -08:00
+++ edited/drivers/video/fbmem.c	2005-01-19 14:52:06 -08:00
@@ -35,6 +35,7 @@
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/device.h>
+#include <linux/efi.h>
 
 #if defined(__mc68000__) || defined(CONFIG_APUS)
 #include <asm/setup.h>
@@ -950,9 +951,13 @@
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 #elif defined(__hppa__)
 	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
-#elif defined(__ia64__) || defined(__arm__) || defined(__sh__) || \
-      defined(__m32r__)
+#elif defined(__arm__) || defined(__sh__) || defined(__m32r__)
 	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+#elif defined(__ia64__)
+	if (efi_range_is_wc(vma->vm_start, vma->vm_end - vma->vm_start))
+		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+	else
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 #else
 #warning What do we have to do here??
 #endif
===== include/linux/efi.h 1.12 vs edited =====
--- 1.12/include/linux/efi.h	2004-11-18 23:03:10 -08:00
+++ edited/include/linux/efi.h	2005-01-19 14:04:14 -08:00
@@ -305,6 +305,27 @@
 extern int __init efi_set_rtc_mmss(unsigned long nowtime);
 extern struct efi_memory_map memmap;
 
+/**
+ * efi_range_is_wc - check the WC bit on an address range
+ * @start: starting kvirt address
+ * @len: length of range
+ *
+ * Consult the EFI memory map and make sure it's ok to set this range WC.
+ * Returns true or false.
+ */
+static inline int efi_range_is_wc(unsigned long start, unsigned long len)
+{
+	int i;
+
+	for (i = 0; i < len; i += (1UL << EFI_PAGE_SHIFT)) {
+		unsigned long paddr = __pa(start + i);
+		if (!(efi_mem_attributes(paddr) & EFI_MEMORY_WC))
+			return 0;
+	}
+	/* The range checked out */
+	return 1;
+}
+
 #ifdef CONFIG_EFI_PCDP
 extern int __init efi_setup_pcdp_console(char *);
 #endif

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