Re: [PATCH 1/2] spi: cadence-quadspi: Disable Auto-HW polling

[Apurva Nandan]

On 14-Jul-21 9:58 PM, Mark Brown wrote:
> On Wed, Jul 14, 2021 at 06:52:12PM +0530, Nandan, Apurva wrote:
>> On 13-Jul-21 11:55 PM, Mark Brown wrote:
>>> On Tue, Jul 13, 2021 at 12:57:41PM +0000, Apurva Nandan wrote:
> 
>>>> cadence-quadspi controller doesn't allow an address phase when
>>>> auto-polling the busy bit on the status register. Unlike SPI NOR
> 
>>> Would it not be better to only disable this on NAND rather than
>>> disabling it completely?
> 
>> I am not sure how it is possible currently in the controller, could you
>> please suggest a way? Also, should we have this logic of checking flash
>> device type in the cadence-quadspi controller? SPI controller should be
>> generic to all flash cores right?
> 
> Surely the controller can tell if an address phase (or other unsupported
> feature) is present?
> 

Yeah sure, understood.

>> In my opinion, it shouldn't harm as spi-nor core doesn't depend on HW
>> polling anyways and auto-HW polling is a minor overhead.
> 
> Flash stuff seems to quite often end up happening when the system is
> heavily loaded for other reasons, it's much more of an issue with things
> that are done more with PIO but still seems useful to avoid having to
> poll in software, either it'll reduce CPU load or reduce latency and
> increase throughput.
> 

Yes, got the point. Will amend it.

Thanks,
Apurva Nandan