@@ -392,7 +392,7 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size)
page_start = start - offset_in_page(start);
page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);
- prot = pgprot_noncached(PAGE_KERNEL);
+ prot = pgprot_writecombine(PAGE_KERNEL);
pages = kmalloc(sizeof(struct page *) * page_count, GFP_KERNEL);
if (!pages) {
@@ -422,7 +422,7 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size)
buffer_start_add = buffer_start_add_locked;
buffer_size_add = buffer_size_add_locked;
- return ioremap(start, size);
+ return ioremap_wc(start, size);
}
static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
This is a note to let you know that I have just added a patch titled pstore-ram: Fix hangs by using write-combine mappings to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11-ckt15. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From fb1b630b6dd09c791fc65d1228de6fd72610a85b Mon Sep 17 00:00:00 2001 From: Rob Herring <robherring2@gmail.com> Date: Fri, 12 Sep 2014 11:32:24 -0700 Subject: pstore-ram: Fix hangs by using write-combine mappings commit 7ae9cb81933515dc7db1aa3c47ef7653717e3090 upstream. Currently trying to use pstore on at least ARMs can hang as we're mapping the peristent RAM with pgprot_noncached(). On ARMs, pgprot_noncached() will actually make the memory strongly ordered, and as the atomic operations pstore uses are implementation defined for strongly ordered memory, they may not work. So basically atomic operations have undefined behavior on ARM for device or strongly ordered memory types. Let's fix the issue by using write-combine variants for mappings. This corresponds to normal, non-cacheable memory on ARM. For many other architectures, this change does not change the mapping type as by default we have: The reason why pgprot_noncached() was originaly used for pstore is because Colin Cross <ccross@android.com> had observed lost debug prints right before a device hanging write operation on some systems. For the platforms supporting pgprot_noncached(), we can add a an optional configuration option to support that. But let's get pstore working first before adding new features. Cc: Arnd Bergmann <arnd@arndb.de> Cc: Anton Vorontsov <cbouatmailru@gmail.com> Cc: Colin Cross <ccross@android.com> Cc: Olof Johansson <olof@lixom.net> Cc: linux-kernel@vger.kernel.org Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Rob Herring <rob.herring@calxeda.com> [tony@atomide.com: updated description] Signed-off-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/pstore/ram_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 1.9.1