linux-kernel - Re: [PATCH] cpufreq: tegra: add regulator dependency for T124

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Message-ID: <20151209021617.GQ3692@ubuntu>
Date:	Wed, 9 Dec 2015 07:46:17 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, broonie@...nel.org,
	Liam Girdwood <lgirdwood@...il.com>
Subject: Re: [PATCH] cpufreq: tegra: add regulator dependency for T124

On 08-12-15, 22:52, Arnd Bergmann wrote:
> This driver is the only one that calls regulator_sync_voltage(), but it
> can currently be built with CONFIG_REGULATOR disabled, producing
> this build error:
> 
> drivers/cpufreq/tegra124-cpufreq.c: In function 'tegra124_cpu_switch_to_pllx':
> drivers/cpufreq/tegra124-cpufreq.c:68:2: error: implicit declaration of function 'regulator_sync_voltage' [-Werror=implicit-function-declaration]
>   regulator_sync_voltage(priv->vdd_cpu_reg);
> 
> My first attempt was to implement a helper for this function
> for regulator_sync_voltage, but Mark Brown explained:
> 
>    We don't do this for *all* regulator API functions - there's some where
>    using them strongly suggests that there is actually a dependency on
>    the regulator API.  This does seem like it might be falling into the
>    specialist category [...]
>    Looking at the code I'm pretty unclear on what the authors think the
>    use of _sync_voltage() is doing in the first place so it may be even
>    better to just remove the call.  It seems to have been included in the
>    first commit so there's not changelog explaining things and there's
>    no comment either.  I'd *expect* it to be a noop as far as I can see.
> 
> This adds the dependency to make the driver always build successfully
> or not be enabled at all. Alternatively, we could investigate if the
> driver should stop calling regulator_sync_voltage instead.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 235a1ba73d92..b1f8a73e5a94 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -226,7 +226,7 @@ config ARM_TEGRA20_CPUFREQ
>  
>  config ARM_TEGRA124_CPUFREQ
>  	tristate "Tegra124 CPUFreq support"
> -	depends on ARCH_TEGRA && CPUFREQ_DT
> +	depends on ARCH_TEGRA && CPUFREQ_DT && REGULATOR
>  	default y
>  	help
>  	  This adds the CPUFreq driver support for Tegra124 SOCs.

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh
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