RE: [PATCH v8 2/2] clocksource: Add Intel Keem Bay timer support

Sanil, Shruthi
2022-03-03T06:18:22Z

Regards,
Shruthi

> -----Original Message-----
> From: Daniel Lezcano <daniel.lezcano@linaro.org>
> Sent: Wednesday, March 2, 2022 9:57 PM
> To: Sanil, Shruthi <shruthi.sanil@intel.com>; tglx@linutronix.de;
> robh+dt@kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org
> Cc: andriy.shevchenko@linux.intel.com; mgross@linux.intel.com; Thokala,
> Srikanth <srikanth.thokala@intel.com>; Raja Subramanian, Lakshmi Bai
> <lakshmi.bai.raja.subramanian@intel.com>; Sangannavar, Mallikarjunappa
> <mallikarjunappa.sangannavar@intel.com>
> Subject: Re: [PATCH v8 2/2] clocksource: Add Intel Keem Bay timer support
>
> On 02/03/2022 17:07, Sanil, Shruthi wrote:
> >> -----Original Message----- From: Daniel Lezcano
> >> <daniel.lezcano@linaro.org> Sent: Wednesday, March 2, 2022 3:54 PM
> >> To: Sanil, Shruthi <shruthi.sanil@intel.com>; tglx@linutronix.de;
> >> robh+dt@kernel.org; linux-kernel@vger.kernel.org;
> >> devicetree@vger.kernel.org Cc: andriy.shevchenko@linux.intel.com;
> >> mgross@linux.intel.com; Thokala, Srikanth
> >> <srikanth.thokala@intel.com>; Raja Subramanian, Lakshmi Bai
> >> <lakshmi.bai.raja.subramanian@intel.com>; Sangannavar,
> >> Mallikarjunappa <mallikarjunappa.sangannavar@intel.com> Subject:
> >> Re: [PATCH v8 2/2] clocksource: Add Intel Keem Bay timer support
> >>
> >> On 02/03/2022 11:12, Sanil, Shruthi wrote:
> >>
> >> [ ... ]
> >>
> >>>>> + if (!(val & TIM_CONFIG_PRESCALER_ENABLE)) { +
> >>>>> pr_err("%pOF: Prescaler is not enabled\n", np); + ret =
> >>>>> -ENODEV; + }
> >>>>
> >>>> Why bail out instead of enabling the prescalar ?
> >>>
> >>> Because it is a secure register and it would be updated by the
> >>> bootloader.
> >> Should it be considered as a firmware bug ?
> >
> > No. This is a common driver across products in the series and
> > enablement of this bit depends on the project requirements. Hence to
> > be sure from driver, we added this check to avoid initialization of
> > the driver in the case where it cannot be functional.
>
> I'm not sure to get the meaning of 'project requirements' but (for my
> understanding) why not describe the timer in the DT for such projects?
>

OK, I understand your point now. We can control the driver initialization from device tree binding rather than add a check in the driver.
But isn't it good to have a check, if enabling of the bit is missed out in the FW? This can help in debugging.

>
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