linux-kernel - Re: [PATCH V3 9/9] PM / OPP: Don't assume platform doesn't have regulators

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Message-ID: <20161110011728.GV16026@codeaurora.org>
Date:   Wed, 9 Nov 2016 17:17:28 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, nm@...com,
        Viresh Kumar <vireshk@...nel.org>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>, robh@...nel.org,
        d-gerlach@...com, broonie@...nel.org
Subject: Re: [PATCH V3 9/9] PM / OPP: Don't assume platform doesn't have
 regulators

On 10/26, Viresh Kumar wrote:
> If the regulators aren't set explicitly by the platform, the OPP core
> assumes that the platform doesn't have any regulator and uses the
> clk-only callback.
> 
> If the platform failed to register a regulator with the core, then this
> can turn out to be a dangerous assumption as the OPP core will try to
> change clk without changing regulators.
> 
> Handle that properly by making sure that the DT didn't had any entries

s/had/have/

> for supply voltages as well.
> 
> diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
> index 3298fac01bb0..34cd48dfe89e 100644
> --- a/drivers/base/power/opp/core.c
> +++ b/drivers/base/power/opp/core.c
> @@ -734,7 +734,17 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
>  
>  	/* Only frequency scaling */
>  	if (!regulators) {
> -		rcu_read_unlock();
> +		/*
> +		 * DT contained supply ratings? Consider platform failed to set
> +		 * regulators.
> +		 */
> +		if (unlikely(opp->supplies[0].u_volt)) {
> +			rcu_read_unlock();
> +			dev_err(dev, "%s: Regulator not registered with OPP core\n",
> +				__func__);
> +			return -EINVAL;
> +		}
> +

Don't we need an rcu_read_unlock() here as well?

>  		return _generic_set_opp_clk_only(dev, clk, old_freq, freq);
>  	}
>  

-- 
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