Re: [PATCH V3 7/8] spi: spi-qcom-qspi: Add interconnect support

[Georgi Djakov <georgi.djakov@linaro.org>]

Hi Akash,

On 4/8/20 15:17, Akash Asthana wrote:
> Hi Mark, Evan, Georgi,
> 
> On 4/7/2020 4:25 PM, Mark Brown wrote:
>> On Tue, Apr 07, 2020 at 03:24:42PM +0530, Akash Asthana wrote:
>>> On 3/31/2020 4:53 PM, Mark Brown wrote:
>>>>> +    ctrl->avg_bw_cpu = Bps_to_icc(speed_hz);
>>>>> +    ctrl->peak_bw_cpu = Bps_to_icc(2 * speed_hz);
>>>> I thought you were going to factor this best guess handling of peak
>>>> bandwidth out into the core?
>>> I can centralize this for SPI, I2C and UART  in Common driver(QUP wrapper)
>>> but still for QSPI I have to keep this piece of code as is because It is not
>>> child of QUP wrapper(it doesn't use common code).
>> Why not?
>>
>>> I am not sure whether I can move this " Assume peak_bw as twice of avg_bw if
>>> nothing is mentioned explicitly" to ICC core because the factor of 2 is
>>> chosen randomly by me.
>> That's the whole point - if this is just a random number then we may as
>> well at least be consistently random.
> 
> Can we centralize below logic of peak_bw selection for all the clients to ICC core?

I don't think this is a good idea for now, because this is very hardware
specific. A scaling factor that works for one client might not work for another.

My questions here is how did you decide on this "multiply by two"? I can imagine
that the traffic can be bursty on some interfaces, but is the factor here really
a "random number" or is this based on some data patterns or performance
analysis?

Thanks,
Georgi