diff options
| author | Tony Lindgren | 2014-09-16 13:50:01 -0700 |
|---|---|---|
| committer | Tony Luck | 2014-12-11 13:38:31 -0800 |
| commit | 027bc8b08242c59e19356b4b2c189f2d849ab660 (patch) | |
| tree | 4bd5ad81fef12692af2c9d278f14903d15ddfb60 /Documentation | |
| parent | 7ae9cb81933515dc7db1aa3c47ef7653717e3090 (diff) | |
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>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ramoops.txt | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt index 69b3cac4749d..5d8675615e59 100644 --- a/Documentation/ramoops.txt +++ b/Documentation/ramoops.txt @@ -14,11 +14,19 @@ survive after a restart. 1. Ramoops concepts -Ramoops uses a predefined memory area to store the dump. The start and size of -the memory area are set using two variables: +Ramoops uses a predefined memory area to store the dump. The start and size +and type of the memory area are set using three variables: * "mem_address" for the start * "mem_size" for the size. The memory size will be rounded down to a power of two. + * "mem_type" to specifiy if the memory type (default is pgprot_writecombine). + +Typically the default value of mem_type=0 should be used as that sets the pstore +mapping to pgprot_writecombine. Setting mem_type=1 attempts to use +pgprot_noncached, which only works on some platforms. This is because pstore +depends on atomic operations. At least on ARM, pgprot_noncached causes the +memory to be mapped strongly ordered, and atomic operations on strongly ordered +memory are implementation defined, and won't work on many ARMs such as omaps. The memory area is divided into "record_size" chunks (also rounded down to power of two) and each oops/panic writes a "record_size" chunk of @@ -55,6 +63,7 @@ Setting the ramoops parameters can be done in 2 different manners: static struct ramoops_platform_data ramoops_data = { .mem_size = <...>, .mem_address = <...>, + .mem_type = <...>, .record_size = <...>, .dump_oops = <...>, .ecc = <...>, |