diff mbox

[v11,12/12] drivers/block/pmem: Map NVDIMM with ioremap_wt()

Message ID 1432940350-1802-13-git-send-email-toshi.kani@hp.com (mailing list archive)
State Superseded
Headers show

Commit Message

Toshi Kani May 29, 2015, 10:59 p.m. UTC 
From: Toshi Kani <toshi.kani@hp.com>

The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
write back the contents of the CPU caches in case of a crash.

This patch changes to use ioremap_wt(), which provides uncached
writes but cached reads, for improving read performance.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
 drivers/block/pmem.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Dan Williams May 30, 2015, 1:18 a.m. UTC | #1 
On Fri, May 29, 2015 at 3:59 PM, Toshi Kani <toshi.kani@hp.com> wrote:
> From: Toshi Kani <toshi.kani@hp.com>
>
> The pmem driver maps NVDIMM with ioremap_nocache() as we cannot
> write back the contents of the CPU caches in case of a crash.
>
> This patch changes to use ioremap_wt(), which provides uncached
> writes but cached reads, for improving read performance.
>
> Signed-off-by: Toshi Kani <toshi.kani@hp.com>

Acked-by: Dan Williams <dan.j.williams@intel.com>

...with the caveat that I'm going to follow in behind this series with
generic ioremap_cache() enabling and converting pmem to use
persistent_copy() / persistent_sync() when the arch/cpu has persistent
memory synchronization instructions.  After the conversion
ioremap_wt() will still be there for the non-persistent_sync() capable
case.
diff mbox

Patch

diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
index eabf4a8..095dfaa 100644
--- a/drivers/block/pmem.c
+++ b/drivers/block/pmem.c
@@ -139,11 +139,11 @@  static struct pmem_device *pmem_alloc(struct device *dev, struct resource *res)
 	}
 
 	/*
-	 * Map the memory as non-cachable, as we can't write back the contents
+	 * Map the memory as write-through, as we can't write back the contents
 	 * of the CPU caches in case of a crash.
 	 */
 	err = -ENOMEM;
-	pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem->size);
+	pmem->virt_addr = ioremap_wt(pmem->phys_addr, pmem->size);
 	if (!pmem->virt_addr)
 		goto out_release_region;