linux-kernel - Re: [PATCH 2/2] cpufreq: arm_scmi: Set fast_switch

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Date:   Wed, 17 Jun 2020 13:47:53 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Nicola Mazzucato <nicola.mazzucato@....com>,
        viresh.kumar@...aro.org
Cc:     linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        lukasz.luba@....com, Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH 2/2] cpufreq: arm_scmi: Set fast_switch_possible
 conditionally

On Wed, Jun 17, 2020 at 10:43:32AM +0100, Nicola Mazzucato wrote:
> Currently the fast_switch_possible flag is set unconditionally
> to true. Based on this, schedutil does not create a
> thread for frequency switching and would always use the
> fast switch path.
> However, if the platform does not support frequency
> fast switch, this may cause the governor to attempt an
> operation that is not supported by the platform.
>
> Fix this by correctly retrieve the fast_switch capability
> from the driver which knows if the platform can support
> this feature.
>

Hi Viresh,

This is first step towards avoiding polling based cpufreq set if firmware
has fast access registers that bypass normal mailbox based messaging.

If you happy with this and provide ack, I will take this along with scmi
changes via ARM SoC. Hope that is fine by you.

--
Regards,
Sudeep