cpufreq: add driver for Raspberry Pi

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.

Also, as the firmware interface might be configured as a module, making
the cpu clock unavailable during init, this implements a full fledged
driver, as opposed to most drivers registering cpufreq-dt, which only
make use of an init routine.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 982efdf9c7e504cee381e824ed60dfdb7440c3cd..2499d0bccb3a991befa26d806650e008376c5c00 100644 (file)
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -141,6 +141,14 @@ config ARM_QCOM_CPUFREQ_HW
          The driver implements the cpufreq interface for this HW engine.
          Say Y if you want to support CPUFreq HW.
 
+config ARM_RASPBERRYPI_CPUFREQ
+       tristate "Raspberry Pi cpufreq support"
+       depends on CLK_RASPBERRYPI || COMPILE_TEST
+       help
+         This adds the CPUFreq driver for Raspberry Pi
+
+         If in doubt, say N.
+
 config ARM_S3C_CPUFREQ
        bool
        help

diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 7bcda2273d0cc809f3348b949764f7208bac73dd..5a6c70d26c98589ff06c9fe00ae43c190d072b3c 100644 (file)
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_ARM_PXA2xx_CPUFREQ)      += pxa2xx-cpufreq.o
 obj-$(CONFIG_PXA3xx)                   += pxa3xx-cpufreq.o
 obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW)      += qcom-cpufreq-hw.o
 obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO)    += qcom-cpufreq-kryo.o
+obj-$(CONFIG_ARM_RASPBERRYPI_CPUFREQ)  += raspberrypi-cpufreq.o
 obj-$(CONFIG_ARM_S3C2410_CPUFREQ)      += s3c2410-cpufreq.o
 obj-$(CONFIG_ARM_S3C2412_CPUFREQ)      += s3c2412-cpufreq.o
 obj-$(CONFIG_ARM_S3C2416_CPUFREQ)      += s3c2416-cpufreq.o

diff --git a/drivers/cpufreq/raspberrypi-cpufreq.c b/drivers/cpufreq/raspberrypi-cpufreq.c
new file mode 100644 (file)
index 0000000..2bc7d97
--- /dev/null
+++ b/drivers/cpufreq/raspberrypi-cpufreq.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Raspberry Pi cpufreq driver
+ *
+ * Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ */
+
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+
+#define RASPBERRYPI_FREQ_INTERVAL      100000000
+
+static struct platform_device *cpufreq_dt;
+
+static int raspberrypi_cpufreq_probe(struct platform_device *pdev)
+{
+       struct device *cpu_dev;
+       unsigned long min, max;
+       unsigned long rate;
+       struct clk *clk;
+       int ret;
+
+       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, NULL);
+       if (IS_ERR(clk)) {
+               dev_err(cpu_dev, "Cannot get clock for CPU0\n");
+               return PTR_ERR(clk);
+       }
+
+       /*
+        * The max and min frequencies are configurable in the Raspberry Pi
+        * firmware, so we query them at runtime.
+        */
+       min = roundup(clk_round_rate(clk, 0), RASPBERRYPI_FREQ_INTERVAL);
+       max = roundup(clk_round_rate(clk, ULONG_MAX), RASPBERRYPI_FREQ_INTERVAL);
+       clk_put(clk);
+
+       for (rate = min; rate <= max; rate += RASPBERRYPI_FREQ_INTERVAL) {
+               ret = dev_pm_opp_add(cpu_dev, rate, 0);
+               if (ret)
+                       goto remove_opp;
+       }
+
+       cpufreq_dt = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
+       ret = PTR_ERR_OR_ZERO(cpufreq_dt);
+       if (ret) {
+               dev_err(cpu_dev, "Failed to create platform device, %d\n", ret);
+               goto remove_opp;
+       }
+
+       return 0;
+
+remove_opp:
+       dev_pm_opp_remove_all_dynamic(cpu_dev);
+
+       return ret;
+}
+
+static int raspberrypi_cpufreq_remove(struct platform_device *pdev)
+{
+       struct device *cpu_dev;
+
+       cpu_dev = get_cpu_device(0);
+       if (cpu_dev)
+               dev_pm_opp_remove_all_dynamic(cpu_dev);
+
+       platform_device_unregister(cpufreq_dt);
+
+       return 0;
+}
+
+/*
+ * 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);
+
+MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de");
+MODULE_DESCRIPTION("Raspberry Pi cpufreq driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:raspberrypi-cpufreq");