Re: [PATCH 08/11] MTD: m25p80: Add option to limit SPI transfer size.

Michal Suchanek
2015-07-15T09:45:07Z

On 4 June 2015 at 19:15, Richard Cochran <richardcochran-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Thu, Jun 04, 2015 at 10:31:45AM +0200, Michal Suchanek wrote:
>> You might want to try to run the bus at 60MHz or 80MHz and then the
>> values would probably again be different.
>>
>> The first two values are set in DT so the logical place for setting
>> the third is also in DT.
>>
>> Otherwise you would need some in-kernel table of these settings.
>
> Or a formula.
>

This formula probably needs to take into account

- the unknown reason for the pl330 to fail transfer
- the device transfer speed and transfer phase as set in DT
- possibly device-specific latency and board-specific trace design
and assembly tolerances

Seriously, until I have at least a vague idea why the transfer fails I
am not comfortable pulling some formula out of thin air and pretending
I have a working patch.

On the other hand, a parameter you can set in the DT and which comes
with a suggested value which can be tuned depending on the system
seems more viable.

Thanks

Michal
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