linux-kernel - Re: [PATCH v2 4/7] cpufreq: add driver for Raspbery Pi

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Date:   Thu, 06 Jun 2019 10:09:48 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Viresh Kumar <viresh.kumar@...aro.org>, stefan.wahren@...e.com
Cc:     mbrugger@...e.de, eric@...olt.net, f.fainelli@...il.com,
        bcm-kernel-feedback-list@...adcom.com, ptesarik@...e.com,
        linux-rpi-kernel@...ts.infradead.org, ssuloev@...altech.com,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        mturquette@...libre.com, linux-pm@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] cpufreq: add driver for Raspbery Pi

Quoting Nicolas Saenz Julienne (2019-06-06 07:22:56)
> diff --git a/drivers/cpufreq/raspberrypi-cpufreq.c b/drivers/cpufreq/raspberrypi-cpufreq.c
> new file mode 100644
> index 000000000000..99b59d5a50aa
> --- /dev/null
> +++ b/drivers/cpufreq/raspberrypi-cpufreq.c
[...]
> +
> +/*
> + * Since the driver depends on clk-raspberrypi, which may return EPROBE_DEFER,
> + * all the activity is performed in the probe, which may be defered as well.
> + */
> +static struct platform_driver raspberrypi_cpufreq_driver = {
> +       .driver = {
> +               .name = "raspberrypi-cpufreq",
> +       },
> +       .probe          = raspberrypi_cpufreq_probe,
> +       .remove         = raspberrypi_cpufreq_remove,
> +};
> +module_platform_driver(raspberrypi_cpufreq_driver);

How does this driver probe? Do you have a node in DT named
raspberrypi-cpufreq that matches and probes this? I would think this
would follow the drivers/cpufreq/cpufreq-dt-platdev.c design where it's
an initcall that probes the board compatible string.

Or, if it depends on clk-raspberrypi probing, maybe it could create the
platform device in that drivers probe function.

> +
> +MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@...e.de");
> +MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:raspberrypi-cpufreq");

I don't think the module alias is needed anymore.