Re: [PATCH V3] spi: spi-geni-qcom: Add SPI driver support for GENI based QUP

[dkota@codeaurora.org]

On 2018-09-10 16:56, Mark Brown wrote:
> On Mon, Sep 10, 2018 at 09:27:09AM +0530, dkota@codeaurora.org wrote:
> 
>> > The thing is, we want it to be 100% reliable, not 99.9% reliable.  Is
>> > it somehow wrong to add the spinlock?  ...or are you noticing
>> > performance problems with the spinlock there?  It's just nice not to
>> > have to think about it.
> 
>> As I said, timeout will be handled after the calculated time as per 
>> data
>> size and speed. Enough time is given for interrupt, there is no chance 
>> of
>> interrupt occurrence during the handle_fifo_timeout(). So there is no 
>> need
>> of spinlock.
> 
> Assuming nothing goes wrong - the system isn't under unusually heavy
> load for example, there's some oversight in the code, there's no impact
> from power management causing things to run more slowly than you were
> expecting, someone uses the driver on a new bit of hardware where there
> are extra considerations or whatever else might go wrong.  Like Doug
> says unless we're in some performance critical situation where it's
> worth thinking *really* hard about how things really are actually safe
> even though they might not look it it's both easier and more
> maintainable to just write software that's obviously safe to 
> inspection.

Agree with this perspective. There wont be any performance impact with 
spinlock. I will include the spinlock in the code.