Re: [PATCH] spi: pl022: Remove timeout in polling mode operation

[Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>]

Hello Linus,

On 15/07/18 12:01, Linus Walleij wrote:
>> Some tests show, that bulk SPI accesses (255 bytes, maximum PL022 can) may
>> take seconds, depending on CPU load. In this case vital SPI accesses can
>> fail because of user-space applications. Some other drivers already do not
>> have timeouts in polling mode.
>>
>> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> Wow what system is this and how does that happen?

we observe this on two different Cortex A15-based SoCs.
One has no DMA implemented in PL022 (axxia), another one has DMA but has no drivers
for it (keystone2).
Therefore both forced to polling mode (PIO mode is much worse because IRQs
can stop process context for seconds if one accesses several megabytes on the MTD
flash in a bulk operation).

> I guess it is fine, but the timeout is there for a reason still. What about
> setting the timeout to a minute or something?

I think it should be fine with some timeout in this order of magnitude, the only
question is, is it enough to make it fixed 60-120 sec or should I introduce a 
Kconfig option with such a default value?

-- 
Best regards,
Alexander Sverdlin.
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