pstore-ram: Allow optional mapping with pgprot_noncached
authorTony Lindgren <tony@atomide.com>
Tue, 16 Sep 2014 20:50:01 +0000 (13:50 -0700)
committerTony Luck <tony.luck@intel.com>
Thu, 11 Dec 2014 21:38:31 +0000 (13:38 -0800)
commit027bc8b08242c59e19356b4b2c189f2d849ab660
tree4bd5ad81fef12692af2c9d278f14903d15ddfb60
parent7ae9cb81933515dc7db1aa3c47ef7653717e3090
pstore-ram: Allow optional mapping with pgprot_noncached

On some ARMs the memory can be mapped pgprot_noncached() and still
be working for atomic operations. As pointed out by Colin Cross
<ccross@android.com>, in some cases you do want to use
pgprot_noncached() if the SoC supports it to see a debug printk
just before a write hanging the system.

On ARMs, the atomic operations on strongly ordered memory are
implementation defined. So let's provide an optional kernel parameter
for configuring pgprot_noncached(), and use pgprot_writecombine() by
default.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robherring2@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: stable@vger.kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Documentation/ramoops.txt
fs/pstore/ram.c
fs/pstore/ram_core.c
include/linux/pstore_ram.h