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

[Dan Williams]

On Fri, May 29, 2015 at 3:59 PM, Toshi Kani  wrote:
> From: Toshi Kani 
>
> 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 

Acked-by: Dan Williams 

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

[Toshi Kani]

From: Toshi Kani 

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 
---
 drivers/block/pmem.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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;
 
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