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SubjectRe: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma
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On 2018-04-03 09:18, Alexandre Belloni wrote:
> On 02/04/2018 at 22:23:17 +0200, Peter Rosin wrote:
>>>> No, but did it again and checked, see transcript below.
>>>
>>> I don't use devmem2. Is 'readback' information accurate or is it
>>> always what's been written? Because when you write 0x33 to 0xFFFFECBC,
>>> 0x33 is read back, but just after that, when you read it again it's 0.
>>
>> Looking at the devmem2 source, it seems very likely that the compiler
>> optimizes out the read and thus outputs what has been written.
>>
>
> At least on x86, it is not optimized out.

Looking at the disassembly, they are gone here (not that I'm fluent).
I then tried to compile devmem2 with -O0 (instead of -Os) and the read
is then fine. So, I guess the devmem2 devs could claim that it's a
buildroot issue, but a volatile would certainly have helped...

Cheers,
Peter

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