linux-kernel - Re: [PATCH v3 13/15] cpufreq: Add cpufreq driver for Tegra124

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Message-ID: <CAKohpokQOALPH13Ykz4nTBOby8J1X6_F30LNKz=gsC4wN3=3vg@mail.gmail.com>
Date:	Tue, 19 Aug 2014 11:25:47 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Tuomas Tynkkynen <tuomas.tynkkynen@....fi>
Cc:	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Paul Walmsley <pwalmsley@...dia.com>,
	Vince Hsu <vinceh@...dia.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Tuomas Tynkkynen <ttynkkynen@...dia.com>
Subject: Re: [PATCH v3 13/15] cpufreq: Add cpufreq driver for Tegra124

On 19 August 2014 09:03, Tuomas Tynkkynen <tuomas.tynkkynen@....fi> wrote:
> From: Tuomas Tynkkynen <ttynkkynen@...dia.com>
>
> Add a new cpufreq driver for Tegra124. Instead of using the PLLX as
> the CPU clocksource, switch immediately to the DFLL. It allows the use
> of higher clock rates, and will automatically scale the CPU voltage as
> well. Besides the CPU clocksource switch, we let the cpufreq-cpu0 driver
> for all the cpufreq operations.
>
> This driver also relies on the DFLL driver to fill the OPP table for the
> CPU0 device, so that the cpufreq-cpu0 driver knows what frequencies to
> use.
>
> Signed-off-by: Tuomas Tynkkynen <ttynkkynen@...dia.com>
> ---
> v3:
>  - separate Kconfig entry

Gud..

>  - use 'select GENERIC_CPUFREQ_CPU0', not depends

Bad :(

It *has* to be a depends here, its not optional. That was outcome of the
chat we had last time, if I remember it well..

>  - support unbinding of the platform device
>  - allocate a state structure instead of globals
>  - use of_match_machine()
>  - various style nits fixed
> ---

You don't need to add these --- here, just add a blank line and git
will take care of things for you :)

>  drivers/cpufreq/Kconfig.arm        |   8 ++
>  drivers/cpufreq/Makefile           |   1 +
>  drivers/cpufreq/tegra124-cpufreq.c | 206 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 215 insertions(+)
>  create mode 100644 drivers/cpufreq/tegra124-cpufreq.c
>
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 3795a16..07bfed1 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -247,3 +247,11 @@ config ARM_TEGRA20_CPUFREQ
>         default y
>         help
>           This adds the CPUFreq driver support for Tegra20 SOCs.
> +
> +config ARM_TEGRA124_CPUFREQ
> +       bool "Tegra124 CPUFreq support"
> +       depends on ARCH_TEGRA
> +       select GENERIC_CPUFREQ_CPU0

So it will become: depends on ARCH_TEGRA && GENERIC_CPUFREQ_CPU0

> +static int tegra124_cpufreq_probe(struct platform_device *pdev)
> +{

> +       priv->vdd_cpu_reg = regulator_get(get_cpu_device(0), "vdd-cpu");

get_cpu_device() can fail as well, and so you may want to check its return
value as well..

> +static int __init tegra_cpufreq_init(void)
> +{
> +       int ret;
> +       struct platform_device *pdev;
> +
> +       if (!of_match_machine(soc_of_matches))
> +               return -ENODEV;

You may want to add a comment here on why you chose to add another layer
of platform device/driver.. i.e. to catch -EPROBE_DEFER from clk-APIs..

> +       ret = platform_driver_register(&tegra124_cpufreq_platdrv);
> +       if (ret)
> +               return ret;
> +
> +       pdev = platform_device_register_simple("cpufreq-tegra124", -1, NULL, 0);
> +       if (IS_ERR(pdev)) {
> +               platform_driver_unregister(&tegra124_cpufreq_platdrv);
> +               return PTR_ERR(pdev);
> +       }
> +
> +       return 0;
> +}
> +module_init(tegra_cpufreq_init);
> +
> +MODULE_AUTHOR("Tuomas Tynkkynen <ttynkkynen@...dia.com>");
> +MODULE_DESCRIPTION("cpufreq driver for NVIDIA Tegra124");
> +MODULE_LICENSE("GPL v2");
> --
> 1.8.1.5
>
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