This patch updates the PAT documentation file to cover the new
WT mapping interfaces.
Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
---
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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