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Date: Mon, 20 May 2019 10:09:53 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc: stefan.wahren@...e.com, "Rafael J. Wysocki" <rjw@...ysocki.net>,
mbrugger@...e.de, sboyd@...nel.org, eric@...olt.net,
f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
ptesarik@...e.com, linux-rpi-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [RFC 5/5] cpufreq: add driver for Raspbery Pi
On 17-05-19, 17:35, Nicolas Saenz Julienne wrote:
> Raspberry Pi's firmware offers and interface though which update it's
> performance requirements. It allows us to request for specific runtime
> frequencies, which the firmware might or might not respect, depending on
> the firmware configuration and thermals.
>
> As the maximum and minimum frequencies are configurable in the firmware
> there is no way to know in advance their values. So the Raspberry Pi
> cpufreq driver queries them, builds an opp frequency table to then
> launch cpufreq-dt.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> ---
> drivers/cpufreq/Kconfig.arm | 8 +++
> drivers/cpufreq/Makefile | 1 +
> drivers/cpufreq/raspberrypi-cpufreq.c | 79 +++++++++++++++++++++++++++
> 3 files changed, 88 insertions(+)
> create mode 100644 drivers/cpufreq/raspberrypi-cpufreq.c
>
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 179a1d302f48..70e5f13f7632 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -308,3 +308,11 @@ config ARM_PXA2xx_CPUFREQ
> This add the CPUFreq driver support for Intel PXA2xx SOCs.
>
> If in doubt, say N.
> +
> +config ARM_RASPBERRYPI_CPUFREQ
> + tristate "Raspberry Pi cpufreq support"
> + depends on RASPBERRYPI_FIRMWARE || (RASPBERRYPI_FIRMWARE=n && COMPILE_TEST)
What about:
depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST
> + help
> + This adds the CPUFreq driver for Raspberry Pi
> +
> + If in doubt, say N.
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index 689b26c6f949..02678e9b2ff5 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -84,6 +84,7 @@ obj-$(CONFIG_ARM_TEGRA124_CPUFREQ) += tegra124-cpufreq.o
> obj-$(CONFIG_ARM_TEGRA186_CPUFREQ) += tegra186-cpufreq.o
> obj-$(CONFIG_ARM_TI_CPUFREQ) += ti-cpufreq.o
> obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ) += vexpress-spc-cpufreq.o
> +obj-$(CONFIG_ARM_RASPBERRYPI_CPUFREQ) += raspberrypi-cpufreq.o
>
>
> ##################################################################################
> diff --git a/drivers/cpufreq/raspberrypi-cpufreq.c b/drivers/cpufreq/raspberrypi-cpufreq.c
> new file mode 100644
> index 000000000000..53cb3e5a8457
> --- /dev/null
> +++ b/drivers/cpufreq/raspberrypi-cpufreq.c
> @@ -0,0 +1,79 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Raspberry Pi cpufreq driver
> + *
> + * Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> + */
> +
> +#include <linux/of.h>
> +#include <linux/clk.h>
> +#include <linux/cpu.h>
> +#include <linux/module.h>
> +#include <linux/pm_opp.h>
> +#include <linux/cpufreq.h>
> +#include <linux/platform_device.h>
> +
> +static const struct of_device_id machines[] __initconst = {
> + { .compatible = "raspberrypi,3-model-b-plus" },
> + { .compatible = "raspberrypi,3-model-b" },
> + { /* sentinel */ }
> +};
> +
> +static int __init raspberrypi_cpufreq_driver_init(void)
> +{
> + struct platform_device *pdev;
> + struct cpumask shared_cpus;
> + struct device *cpu_dev;
> + struct clk *clk;
> + long min, max;
> + long rate;
> + int ret;
> +
> + if (!of_match_node(machines, of_root))
> + return -ENODEV;
> +
> + cpu_dev = get_cpu_device(0);
> + if (!cpu_dev) {
> + pr_err("Cannot get CPU for cpufreq driver\n");
> + return -ENODEV;
> + }
> +
> + clk = clk_get(cpu_dev, 0);
> + if (IS_ERR(clk)) {
> + dev_err(cpu_dev, "Cannot get clock for CPU0\n");
> + return PTR_ERR(clk);
> + }
You want to do a clk_put() somewhere ?
> +
> + /*
> + * The max and min frequencies are configurable in the Raspberry Pi
> + * firmware, so we query them at runtime
> + */
> + min = clk_round_rate(clk, 0);
> + max = clk_round_rate(clk, ULONG_MAX);
> +
> + for (rate = min; rate < max; rate += 100000000) {
> + ret = dev_pm_opp_add(cpu_dev, rate, 0);
> + if (ret)
> + return ret;
> + }
> +
> + ret = dev_pm_opp_add(cpu_dev, max, 0);
> + if (ret)
> + return ret;
On errors, you should remove all previously added OPPs.
> +
> + cpumask_setall(&shared_cpus);
> + dev_pm_opp_set_sharing_cpus(cpu_dev, &shared_cpus);
Why are these required? This must be done by the cpufreq-dt driver anyway ?
> +
> + pdev = platform_device_register_data(NULL, "cpufreq-dt", -1, NULL, 0);
> + ret = PTR_ERR_OR_ZERO(pdev);
> + if (ret)
> + dev_err(cpu_dev, "Failed to create platform device, %d\n", ret);
> +
> + return ret;
> +}
> +
> +late_initcall(raspberrypi_cpufreq_driver_init);
> +
> +MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@...e.de");
> +MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.21.0
--
viresh
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