linux-kernel - [PATCH v2 6/6] x86, pat: Update documentation for WT changes

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Date:	Wed, 10 Sep 2014 10:51:50 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, arnd@...db.de
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org, jgross@...e.com,
	stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br,
	yigal@...xistor.com, konrad.wilk@...cle.com,
	Toshi Kani <toshi.kani@...com>
Subject: [PATCH v2 6/6] x86, pat: Update documentation for WT changes

This patch updates the PAT documentation file to cover the new
WT mapping interfaces.

Signed-off-by: Toshi Kani <toshi.kani@...com>
---
 Documentation/x86/pat.txt |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt
index cf08c9f..445caab 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
@@ -38,12 +38,17 @@ ioremap_nocache        |    --    |    UC-     |       UC-        |
                        |          |            |                  |
 ioremap_wc             |    --    |    --      |       WC         |
                        |          |            |                  |
+ioremap_wt             |    --    |    --      |       WT         |
+                       |          |            |                  |
 set_memory_uc          |    UC-   |    --      |       --         |
  set_memory_wb         |          |            |                  |
                        |          |            |                  |
 set_memory_wc          |    WC    |    --      |       --         |
  set_memory_wb         |          |            |                  |
                        |          |            |                  |
+set_memory_wt          |    *1    |    --      |       WT         |
+ set_memory_wb         |          |            |                  |
+                       |          |            |                  |
 pci sysfs resource     |    --    |    --      |       UC-        |
                        |          |            |                  |
 pci sysfs resource_wc  |    --    |    --      |       WC         |
@@ -79,6 +84,7 @@ pci proc               |    --    |    --      |       WC         |
  MTRR says !WB         |          |            |                  |
                        |          |            |                  |
 -------------------------------------------------------------------
+*1: -EINVAL due to the current limitation in reserve_memtype().
 
 Advanced APIs for drivers
 -------------------------
@@ -115,8 +121,8 @@ can be more restrictive, in case of any existing aliasing for that address.
 For example: If there is an existing uncached mapping, a new ioremap_wc can
 return uncached mapping in place of write-combine requested.
 
-set_memory_[uc|wc] and set_memory_wb should be used in pairs, where driver will
-first make a region uc or wc and switch it back to wb after use.
+set_memory_[uc|wc|wt] and set_memory_wb should be used in pairs, where driver
+will first make a region uc, wc or wt and switch it back to wb after use.
 
 Over time writes to /proc/mtrr will be deprecated in favor of using PAT based
 interfaces. Users writing to /proc/mtrr are suggested to use above interfaces.
@@ -126,6 +132,8 @@ types.
 
 Drivers should use set_memory_[uc|wc] to set access type for RAM ranges.
 
+Drivers may map the entire NV-DIMM range with ioremap_cache and then change
+a specific range to wt with set_memory_wt.
 
 PAT debugging
 -------------
--
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