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[1/2] Documentation: arm: early_ioremap

Message ID 1372182401-11029-2-git-send-email-leif.lindholm@linaro.org
State New
Headers show

Commit Message

Leif Lindholm June 25, 2013, 5:46 p.m. UTC 
This patch provides documentation of the early_ioremap() functionality,
including its implementation and usage instructions.

Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
---
 Documentation/arm/00-INDEX          |    2 ++
 Documentation/arm/early_ioremap.txt |   12 ++++++++++++
 2 files changed, 14 insertions(+)
 create mode 100644 Documentation/arm/early_ioremap.txt
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Patch

diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX
index 36420e1..4978456 100644
--- a/Documentation/arm/00-INDEX
+++ b/Documentation/arm/00-INDEX
@@ -24,6 +24,8 @@  SPEAr
 	- ST SPEAr platform Linux Overview
 VFP/
 	- Release notes for Linux Kernel Vector Floating Point support code
+early_ioremap.txt
+	- documentation of the early_ioremap() functionality
 empeg/
 	- Ltd's Empeg MP3 Car Audio Player
 mem_alignment
diff --git a/Documentation/arm/early_ioremap.txt b/Documentation/arm/early_ioremap.txt
new file mode 100644
index 0000000..178f791
--- /dev/null
+++ b/Documentation/arm/early_ioremap.txt
@@ -0,0 +1,12 @@ 
+early_ioremap() and early_iounmap() rovide a mechanism for temporarily mapping
+in small blocks of memory, identified by their physical address, into the
+fixmap virtual address block before paging_init() has been called and more
+flexible mapping functions are available.
+
+Due to its direct method, it also gets around potential need for special
+handling of regions that end up in highmem.
+
+It supports up to 7 simultaneously mapped regions of up to 128KB each.
+All regions are mapped as non-shareable device memory.
+
+Specify 'early_ioremap_debug' on the kernel commandline for verbose output.