Re: [PATCH v5 6/9] coresight: add support for CPU debug module

Mathieu Poirier
2017-03-30T15:46:21Z

On 29 March 2017 at 19:59, Leo Yan <leo.yan@linaro.org> wrote:
> On Wed, Mar 29, 2017 at 10:55:35AM -0600, Mathieu Poirier wrote:
>
> [...]
>
>> > So this is why add "idle_constraint" as a central place to control
>> > power domain for CPU debug purpose and I also think this is more
>> > friendly for hardware design, e.g. some platforms can enable partial
>> > low power states to save power and avoid overheat after using this
>> > driver.
>> >
>> > How about you think for this?
>>
>> Like Sudeep pointed out we should concentrate on doing the right thing,
>> that is work with EDPRSR.PU, EDPRCR.COREPURQ and EDPRCR.CORENPDRQ.
>
> Agree, and I think we have aligned for this.
>
>> Anything outside of that becomes platform specific and can't be handled in
>> this driver.
>
> Sorry I argue a bit for this just want to make things more clear and
> if can have better method.
>
> Though the issue is platform specific, but the code is to seek common
> method to handle them. So the driver has no any platform specific code.

Seeking a common way to handle platform specific problems doesn't
scale and will never be encompassing. There will always be a quirk
somewhere to deal with, hence the idea of keeping things separate.

>
> I read again for Suziki's suggestion: "4) Should document the fact that,
> on some platforms, the user may have to disable CPUidle explicitly to
> get the driver working. But let us not make it the default. The user
> with a not so ideal platform could add "nohlt" and get it working."

Suzuki and I are expressing the same view using different words.

>
> So I'm not strong to resist and if this is alignment yet, I should
> document well for this but doesn't handle it in driver (keep driver
> simple).
>
> Thanks,
> Leo Yan