linux-kernel - Re: [PATCH 2/2] cpufreq: mediatek: Add MT8173 cpufreq driver

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Message-ID: <20150624085658.GF27188@linux>
Date:	Wed, 24 Jun 2015 14:26:58 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Pi-Cheng Chen <pi-cheng.chen@...aro.org>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/2] cpufreq: mediatek: Add MT8173 cpufreq driver

On 24-06-15, 16:44, Pi-Cheng Chen wrote:
> One reason to put those initialization and resource allocation in probe is
> that it's easier to handle the return value -PROBE_DEFER from clock
> and regulator framework when trying to get clocks and regulators
> consumed by cpufreq driver.

This is the sequence of events if you move these things to ->init().

- your driver's probe()
  -> cpufreq_register_driver()
    -> init()
      -> clk/reg get, failed, return -EPROBE_DEFER

And the failure here will be propagated to probe(). So, it should
work IMHO.

> The other reason is when the whole system is resuming from suspend,
> the other subsystem e.g. i2c on which cpufreq driver depends might not
> ready yet during cpufreq driver initialization. In this case, the cpufreq
> driver will be blocked when trying to get resources e.g. regulator on i2c
> bus, and the whole system will stuck for seconds.

That's something else you must investigate on. This dependency should
be resolved in some other way, I thought DT might have taken care of
such dependencies.

-- 
viresh
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