cpufreq: Add sun50i nvmem based CPU scaling driver

For some SoCs, the CPU frequency subset and voltage value of each OPP
varies based on the silicon variant in use. The sun50i-cpufreq-nvmem
driver reads the efuse value from the SoC to provide the OPP framework
with required information.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

MAINTAINERS

@@ -676,6 +676,13 @@ L:	linux-media@vger.kernel.org
 S:	Maintained
 F:	drivers/staging/media/allegro-dvt/
 
+ALLWINNER CPUFREQ DRIVER
+M:	Yangtao Li <tiny.windzz@gmail.com>
+L:	linux-pm@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/opp/sun50i-nvmem-cpufreq.txt
+F:	drivers/cpufreq/sun50i-cpufreq-nvmem.c
+
 ALLWINNER SECURITY SYSTEM
 M:	Corentin Labbe <clabbe.montjoie@gmail.com>
 L:	linux-crypto@vger.kernel.org

drivers/cpufreq/Kconfig.arm

@@ -19,6 +19,18 @@ config ACPI_CPPC_CPUFREQ
 
 	  If in doubt, say N.
 
+config ARM_ALLWINNER_SUN50I_CPUFREQ_NVMEM
+	tristate "Allwinner nvmem based SUN50I CPUFreq driver"
+	depends on ARCH_SUNXI
+	depends on NVMEM_SUNXI_SID
+	select PM_OPP
+	help
+	  This adds the nvmem based CPUFreq driver for Allwinner
+	  h6 SoC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called sun50i-cpufreq-nvmem.
+
 config ARM_ARMADA_37XX_CPUFREQ
 	tristate "Armada 37xx CPUFreq support"
 	depends on ARCH_MVEBU && CPUFREQ_DT

drivers/cpufreq/Makefile

@@ -80,6 +80,7 @@ obj-$(CONFIG_ARM_SCMI_CPUFREQ)		+= scmi-cpufreq.o
 obj-$(CONFIG_ARM_SCPI_CPUFREQ)		+= scpi-cpufreq.o
 obj-$(CONFIG_ARM_SPEAR_CPUFREQ)		+= spear-cpufreq.o
 obj-$(CONFIG_ARM_STI_CPUFREQ)		+= sti-cpufreq.o
+obj-$(CONFIG_ARM_ALLWINNER_SUN50I_CPUFREQ_NVMEM) += sun50i-cpufreq-nvmem.o
 obj-$(CONFIG_ARM_TANGO_CPUFREQ)		+= tango-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA20_CPUFREQ)	+= tegra20-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA124_CPUFREQ)	+= tegra124-cpufreq.o

drivers/cpufreq/cpufreq-dt-platdev.c

@@ -101,6 +101,8 @@ static const struct of_device_id whitelist[] __initconst = {
  * platforms using "operating-points-v2" property.
  */
 static const struct of_device_id blacklist[] __initconst = {
+	{ .compatible = "allwinner,sun50i-h6", },
+
 	{ .compatible = "calxeda,highbank", },
 	{ .compatible = "calxeda,ecx-2000", },
 

drivers/cpufreq/sun50i-cpufreq-nvmem.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Allwinner CPUFreq nvmem based driver
+ *
+ * The sun50i-cpufreq-nvmem driver reads the efuse value from the SoC to
+ * provide the OPP framework with required information.
+ *
+ * Copyright (C) 2019 Yangtao Li <tiny.windzz@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+
+#define MAX_NAME_LEN	7
+
+#define NVMEM_MASK	0x7
+#define NVMEM_SHIFT	5
+
+static struct platform_device *cpufreq_dt_pdev, *sun50i_cpufreq_pdev;
+
+/**
+ * sun50i_cpufreq_get_efuse() - Parse and return efuse value present on SoC
+ * @versions: Set to the value parsed from efuse
+ *
+ * Returns 0 if success.
+ */
+static int sun50i_cpufreq_get_efuse(u32 *versions)
+{
+	struct nvmem_cell *speedbin_nvmem;
+	struct device_node *np;
+	struct device *cpu_dev;
+	u32 *speedbin, efuse_value;
+	size_t len;
+	int ret;
+
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev)
+		return -ENODEV;
+
+	np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
+	if (!np)
+		return -ENOENT;
+
+	ret = of_device_is_compatible(np,
+				      "allwinner,sun50i-h6-operating-points");
+	if (!ret) {
+		of_node_put(np);
+		return -ENOENT;
+	}
+
+	speedbin_nvmem = of_nvmem_cell_get(np, NULL);
+	of_node_put(np);
+	if (IS_ERR(speedbin_nvmem)) {
+		if (PTR_ERR(speedbin_nvmem) != -EPROBE_DEFER)
+			pr_err("Could not get nvmem cell: %ld\n",
+			       PTR_ERR(speedbin_nvmem));
+		return PTR_ERR(speedbin_nvmem);
+	}
+
+	speedbin = nvmem_cell_read(speedbin_nvmem, &len);
+	nvmem_cell_put(speedbin_nvmem);
+	if (IS_ERR(speedbin))
+		return PTR_ERR(speedbin);
+
+	efuse_value = (*speedbin >> NVMEM_SHIFT) & NVMEM_MASK;
+	switch (efuse_value) {
+	case 0b0001:
+		*versions = 1;
+		break;
+	case 0b0011:
+		*versions = 2;
+		break;
+	default:
+		/*
+		 * For other situations, we treat it as bin0.
+		 * This vf table can be run for any good cpu.
+		 */
+		*versions = 0;
+		break;
+	}
+
+	kfree(speedbin);
+	return 0;
+};
+
+static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
+{
+	struct opp_table **opp_tables;
+	char name[MAX_NAME_LEN];
+	unsigned int cpu;
+	u32 speed = 0;
+	int ret;
+
+	opp_tables = kcalloc(num_possible_cpus(), sizeof(*opp_tables),
+			     GFP_KERNEL);
+	if (!opp_tables)
+		return -ENOMEM;
+
+	ret = sun50i_cpufreq_get_efuse(&speed);
+	if (ret)
+		return ret;
+
+	snprintf(name, MAX_NAME_LEN, "speed%d", speed);
+
+	for_each_possible_cpu(cpu) {
+		struct device *cpu_dev = get_cpu_device(cpu);
+
+		if (!cpu_dev) {
+			ret = -ENODEV;
+			goto free_opp;
+		}
+
+		opp_tables[cpu] = dev_pm_opp_set_prop_name(cpu_dev, name);
+		if (IS_ERR(opp_tables[cpu])) {
+			ret = PTR_ERR(opp_tables[cpu]);
+			pr_err("Failed to set prop name\n");
+			goto free_opp;
+		}
+	}
+
+	cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
+							  NULL, 0);
+	if (!IS_ERR(cpufreq_dt_pdev)) {
+		platform_set_drvdata(pdev, opp_tables);
+		return 0;
+	}
+
+	ret = PTR_ERR(cpufreq_dt_pdev);
+	pr_err("Failed to register platform device\n");
+
+free_opp:
+	for_each_possible_cpu(cpu) {
+		if (IS_ERR_OR_NULL(opp_tables[cpu]))
+			break;
+		dev_pm_opp_put_prop_name(opp_tables[cpu]);
+	}
+	kfree(opp_tables);
+
+	return ret;
+}
+
+static int sun50i_cpufreq_nvmem_remove(struct platform_device *pdev)
+{
+	struct opp_table **opp_tables = platform_get_drvdata(pdev);
+	unsigned int cpu;
+
+	platform_device_unregister(cpufreq_dt_pdev);
+
+	for_each_possible_cpu(cpu)
+		dev_pm_opp_put_prop_name(opp_tables[cpu]);
+
+	kfree(opp_tables);
+
+	return 0;
+}
+
+static struct platform_driver sun50i_cpufreq_driver = {
+	.probe = sun50i_cpufreq_nvmem_probe,
+	.remove = sun50i_cpufreq_nvmem_remove,
+	.driver = {
+		.name = "sun50i-cpufreq-nvmem",
+	},
+};
+
+static const struct of_device_id sun50i_cpufreq_match_list[] = {
+	{ .compatible = "allwinner,sun50i-h6" },
+	{}
+};
+
+static const struct of_device_id *sun50i_cpufreq_match_node(void)
+{
+	const struct of_device_id *match;
+	struct device_node *np;
+
+	np = of_find_node_by_path("/");
+	match = of_match_node(sun50i_cpufreq_match_list, np);
+	of_node_put(np);
+
+	return match;
+}
+
+/*
+ * Since the driver depends on nvmem drivers, which may return EPROBE_DEFER,
+ * all the real activity is done in the probe, which may be defered as well.
+ * The init here is only registering the driver and the platform device.
+ */
+static int __init sun50i_cpufreq_init(void)
+{
+	const struct of_device_id *match;
+	int ret;
+
+	match = sun50i_cpufreq_match_node();
+	if (!match)
+		return -ENODEV;
+
+	ret = platform_driver_register(&sun50i_cpufreq_driver);
+	if (unlikely(ret < 0))
+		return ret;
+
+	sun50i_cpufreq_pdev =
+		platform_device_register_simple("sun50i-cpufreq-nvmem",
+						-1, NULL, 0);
+	ret = PTR_ERR_OR_ZERO(sun50i_cpufreq_pdev);
+	if (ret == 0)
+		return 0;
+
+	platform_driver_unregister(&sun50i_cpufreq_driver);
+	return ret;
+}
+module_init(sun50i_cpufreq_init);
+
+static void __exit sun50i_cpufreq_exit(void)
+{
+	platform_device_unregister(sun50i_cpufreq_pdev);
+	platform_driver_unregister(&sun50i_cpufreq_driver);
+}
+module_exit(sun50i_cpufreq_exit);
+
+MODULE_DESCRIPTION("Sun50i-h6 cpufreq driver");
+MODULE_LICENSE("GPL v2");