Re: [RFC PATCH 1/2] memremap: add arch specific hook for MEMREMAP_WB mappings

[Robert Jarzmik]

Dan Williams <dan.j.williams@xxxxxxxxx> writes:

> On Tue, Feb 23, 2016 at 4:26 AM, Ard Biesheuvel
> <ard.biesheuvel@xxxxxxxxxx> wrote:
>> On 23 February 2016 at 13:03, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>>> On 23 February 2016 at 12:58, Russell King - ARM Linux
>>> <linux@xxxxxxxxxxxxxxxx> 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