x86/mm, asm-generic: Add ioremap_wt() for creating Write-Through mappings

Add ioremap_wt() for creating Write-Through mappings on x86. It
follows the same model as ioremap_wc() for multi-arch support.
Define ARCH_HAS_IOREMAP_WT in the x86 version of io.h to
indicate that ioremap_wt() is implemented on x86.

Also update the PAT documentation file to cover ioremap_wt().

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Elliott@hp.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arnd@arndb.de
Cc: hch@lst.de
Cc: hmh@hmh.eng.br
Cc: jgross@suse.com
Cc: konrad.wilk@oracle.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: linux-nvdimm@lists.01.org
Cc: stefan.bader@canonical.com
Cc: yigal@plexistor.com
Link: http://lkml.kernel.org/r/1433436928-31903-8-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 39 insertions, 1 deletions

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index 521bd8adc3b8..db0de6cfc351 100644
--- a/Documentation/x86/pat.txt
+++ b/Documentation/x86/pat.txt
@@ -12,7 +12,7 @@ virtual addresses.
 
 PAT allows for different types of memory attributes. The most commonly used
 ones that will be supported at this time are Write-back, Uncached,
-Write-combined and Uncached Minus.
+Write-combined, Write-through and Uncached Minus.
 
 
 PAT APIs
@@ -40,6 +40,8 @@ ioremap_nocache        |    --    |    UC-     |       UC-        |
                        |          |            |                  |
 ioremap_wc             |    --    |    --      |       WC         |
                        |          |            |                  |
+ioremap_wt             |    --    |    --      |       WT         |
+                       |          |            |                  |
 set_memory_uc          |    UC-   |    --      |       --         |
  set_memory_wb         |          |            |                  |
                        |          |            |                  |
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index a94463063b46..83ec9b1d77cc 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -35,6 +35,7 @@
   */
 
 #define ARCH_HAS_IOREMAP_WC
+#define ARCH_HAS_IOREMAP_WT
 
 #include <linux/string.h>
 #include <linux/compiler.h>
@@ -320,6 +321,7 @@ extern void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);
 extern int ioremap_change_attr(unsigned long vaddr, unsigned long size,
                                 enum page_cache_mode pcm);
 extern void __iomem *ioremap_wc(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_wt(resource_size_t offset, unsigned long size);
 
 extern bool is_early_ioremap_ptep(pte_t *ptep);
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index cc0f17c5ad9f..07cd46a8f30a 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -172,6 +172,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
                 prot = __pgprot(pgprot_val(prot) |
                                 cachemode2protval(_PAGE_CACHE_MODE_WC));
                 break;
+        case _PAGE_CACHE_MODE_WT:
+                prot = __pgprot(pgprot_val(prot) |
+                                cachemode2protval(_PAGE_CACHE_MODE_WT));
+                break;
         case _PAGE_CACHE_MODE_WB:
                 break;
         }
@@ -297,6 +301,23 @@ void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
 }
 EXPORT_SYMBOL(ioremap_wc);
 
+/**
+ * ioremap_wt   -       map memory into CPU space write through
+ * @phys_addr:  bus address of the memory
+ * @size:       size of the resource to map
+ *
+ * This version of ioremap ensures that the memory is marked write through.
+ * Write through stores data into memory while keeping the cache up-to-date.
+ *
+ * Must be freed with iounmap.
+ */
+void __iomem *ioremap_wt(resource_size_t phys_addr, unsigned long size)
+{
+        return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WT,
+                                        __builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_wt);
+
 void __iomem *ioremap_cache(resource_size_t phys_addr, unsigned long size)
 {
         return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WB,
diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 90ccba7f9f9a..f56094cfdeff 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -785,8 +785,17 @@ static inline void __iomem *ioremap_wc(phys_addr_t offset, size_t size)
 }
 #endif
 
+#ifndef ioremap_wt
+#define ioremap_wt ioremap_wt
+static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
+{
+        return ioremap_nocache(offset, size);
+}
+#endif
+
 #ifndef iounmap
 #define iounmap iounmap
+
 static inline void iounmap(void __iomem *addr)
 {
 }
diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
index 1b41011643a5..d8f8622fa044 100644
--- a/include/asm-generic/iomap.h
+++ b/include/asm-generic/iomap.h
@@ -66,6 +66,10 @@ extern void ioport_unmap(void __iomem *);
 #define ioremap_wc ioremap_nocache
 #endif
 
+#ifndef ARCH_HAS_IOREMAP_WT
+#define ioremap_wt ioremap_nocache
+#endif
+
 #ifdef CONFIG_PCI
 /* Destroy a virtual mapping cookie for a PCI BAR (memory or IO) */
 struct pci_dev;