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SubjectRe: [RFC PATCH 1/2] memremap: add arch specific hook for MEMREMAP_WB mappings
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Dan Williams <dan.j.williams@intel.com> writes:

> On Tue, Feb 23, 2016 at 4:26 AM, Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
>> On 23 February 2016 at 13:03, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>>> On 23 February 2016 at 12:58, Russell King - ARM Linux
>>> <linux@arm.linux.org.uk> wrote:
>>>> On Mon, Feb 22, 2016 at 09:35:24PM +0100, Ard Biesheuvel wrote:
>> OK, I see what you mean. I find it unfortunate that ioremap_cache()
>> instances are blindly being replaced with memremap(), and I wonder if
>> this wasted test by and/or cc'ed to people who can actually test this
>> driver. Dan?

Actually I have the hardware to test it.

And I also know what is behind :
- it's a CFI NOR based memory
- these are Intel StrataFlash 28F128J3A chips
- as a CFI memory it is mapped on the system bus
- from a read perspective, it behaves like a normal memory
- but once the first write reaches the CFI, everything changes (the address
space layout doesn't have the same meaning, be that becoming a status code or
something else).
In these conditions reordering of writes versus reads, merging reads after
a write or coalescing writes is a recipe for disaster.

All of this to say I can make a small discrete number of tests (less than 10
write or erase ones to preserve the precious NOR).

Cheers.

--
Robert

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