cpufreq: st: Provide runtime initialised driver for ST's platforms

The bootloader is charged with the responsibility to provide platform
specific Dynamic Voltage and Frequency Scaling (DVFS) information via
Device Tree.  This driver takes the supplied configuration and
registers it with the new generic OPP framework, to then be used with
CPUFreq.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.arm

@@ -219,6 +219,16 @@ config ARM_SPEAR_CPUFREQ
 	help
 	  This adds the CPUFreq driver support for SPEAr SOCs.
 
+config ARM_STI_CPUFREQ
+	tristate "STi CPUFreq support"
+	depends on SOC_STIH407
+	help
+	  This driver uses the generic OPP framework to match the running
+	  platform with a predefined set of suitable values.  If not provided
+	  we will fall-back so safe-values contained in Device Tree.  Enable
+	  this config option if you wish to add CPUFreq support for STi based
+	  SoCs.
+
 config ARM_TEGRA20_CPUFREQ
 	bool "Tegra20 CPUFreq support"
 	depends on ARCH_TEGRA

drivers/cpufreq/Makefile

@@ -73,6 +73,7 @@ obj-$(CONFIG_ARM_SA1100_CPUFREQ)	+= sa1100-cpufreq.o
 obj-$(CONFIG_ARM_SA1110_CPUFREQ)	+= sa1110-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_TEGRA20_CPUFREQ)	+= tegra20-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA124_CPUFREQ)	+= tegra124-cpufreq.o
 obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ)	+= vexpress-spc-cpufreq.o

drivers/cpufreq/sti-cpufreq.c

@@ -0,0 +1,294 @@
+/*
+ * Match running platform with pre-defined OPP values for CPUFreq
+ *
+ * Author: Ajit Pal Singh <ajitpal.singh@st.com>
+ *         Lee Jones <lee.jones@linaro.org>
+ *
+ * Copyright (C) 2015 STMicroelectronics (R&D) Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the version 2 of the GNU General Public License as
+ * published by the Free Software Foundation
+ */
+
+#include <linux/cpu.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/pm_opp.h>
+#include <linux/regmap.h>
+
+#define VERSION_ELEMENTS	3
+#define MAX_PCODE_NAME_LEN	7
+
+#define VERSION_SHIFT		28
+#define HW_INFO_INDEX		1
+#define MAJOR_ID_INDEX		1
+#define MINOR_ID_INDEX		2
+
+/*
+ * Only match on "suitable for ALL versions" entries
+ *
+ * This will be used with the BIT() macro.  It sets the
+ * top bit of a 32bit value and is equal to 0x80000000.
+ */
+#define DEFAULT_VERSION		31
+
+enum {
+	PCODE = 0,
+	SUBSTRATE,
+	DVFS_MAX_REGFIELDS,
+};
+
+/**
+ * ST CPUFreq Driver Data
+ *
+ * @cpu_node		CPU's OF node
+ * @syscfg_eng		Engineering Syscon register map
+ * @regmap		Syscon register map
+ */
+static struct sti_cpufreq_ddata {
+	struct device *cpu;
+	struct regmap *syscfg_eng;
+	struct regmap *syscfg;
+} ddata;
+
+static int sti_cpufreq_fetch_major(void) {
+	struct device_node *np = ddata.cpu->of_node;
+	struct device *dev = ddata.cpu;
+	unsigned int major_offset;
+	unsigned int socid;
+	int ret;
+
+	ret = of_property_read_u32_index(np, "st,syscfg",
+					 MAJOR_ID_INDEX, &major_offset);
+	if (ret) {
+		dev_err(dev, "No major number offset provided in %s [%d]\n",
+			np->full_name, ret);
+		return ret;
+	}
+
+	ret = regmap_read(ddata.syscfg, major_offset, &socid);
+	if (ret) {
+		dev_err(dev, "Failed to read major number from syscon [%d]\n",
+			ret);
+		return ret;
+	}
+
+	return ((socid >> VERSION_SHIFT) & 0xf) + 1;
+}
+
+static int sti_cpufreq_fetch_minor(void)
+{
+	struct device *dev = ddata.cpu;
+	struct device_node *np = dev->of_node;
+	unsigned int minor_offset;
+	unsigned int minid;
+	int ret;
+
+	ret = of_property_read_u32_index(np, "st,syscfg-eng",
+					 MINOR_ID_INDEX, &minor_offset);
+	if (ret) {
+		dev_err(dev,
+			"No minor number offset provided %s [%d]\n",
+			np->full_name, ret);
+		return ret;
+	}
+
+	ret = regmap_read(ddata.syscfg_eng, minor_offset, &minid);
+	if (ret) {
+		dev_err(dev,
+			"Failed to read the minor number from syscon [%d]\n",
+			ret);
+		return ret;
+	}
+
+	return minid & 0xf;
+}
+
+static int sti_cpufreq_fetch_regmap_field(const struct reg_field *reg_fields,
+					  int hw_info_offset, int field)
+{
+	struct regmap_field *regmap_field;
+	struct reg_field reg_field = reg_fields[field];
+	struct device *dev = ddata.cpu;
+	unsigned int value;
+	int ret;
+
+	reg_field.reg = hw_info_offset;
+	regmap_field = devm_regmap_field_alloc(dev,
+					       ddata.syscfg_eng,
+					       reg_field);
+	if (IS_ERR(regmap_field)) {
+		dev_err(dev, "Failed to allocate reg field\n");
+		return PTR_ERR(regmap_field);
+	}
+
+	ret = regmap_field_read(regmap_field, &value);
+	if (ret) {
+		dev_err(dev, "Failed to read %s code\n",
+			field ? "SUBSTRATE" : "PCODE");
+		return ret;
+	}
+
+	return value;
+}
+
+static const struct reg_field sti_stih407_dvfs_regfields[DVFS_MAX_REGFIELDS] = {
+	[PCODE]		= REG_FIELD(0, 16, 19),
+	[SUBSTRATE]	= REG_FIELD(0, 0, 2),
+};
+
+static const struct reg_field *sti_cpufreq_match(void)
+{
+	if (of_machine_is_compatible("st,stih407") ||
+	    of_machine_is_compatible("st,stih410"))
+		return sti_stih407_dvfs_regfields;
+
+	return NULL;
+}
+
+static int sti_cpufreq_set_opp_info(void)
+{
+	struct device *dev = ddata.cpu;
+	struct device_node *np = dev->of_node;
+	const struct reg_field *reg_fields;
+	unsigned int hw_info_offset;
+	unsigned int version[VERSION_ELEMENTS];
+	int pcode, substrate, major, minor;
+	int ret;
+	char name[MAX_PCODE_NAME_LEN];
+
+	reg_fields = sti_cpufreq_match();
+	if (!reg_fields) {
+		dev_err(dev, "This SoC doesn't support voltage scaling");
+		return -ENODEV;
+	}
+
+	ret = of_property_read_u32_index(np, "st,syscfg-eng",
+					 HW_INFO_INDEX, &hw_info_offset);
+	if (ret) {
+		dev_warn(dev, "Failed to read HW info offset from DT\n");
+		substrate = DEFAULT_VERSION;
+		pcode = 0;
+		goto use_defaults;
+	}
+
+	pcode = sti_cpufreq_fetch_regmap_field(reg_fields,
+					       hw_info_offset,
+					       PCODE);
+	if (pcode < 0) {
+		dev_warn(dev, "Failed to obtain process code\n");
+		/* Use default pcode */
+		pcode = 0;
+	}
+
+	substrate = sti_cpufreq_fetch_regmap_field(reg_fields,
+						   hw_info_offset,
+						   SUBSTRATE);
+	if (substrate) {
+		dev_warn(dev, "Failed to obtain substrate code\n");
+		/* Use default substrate */
+		substrate = DEFAULT_VERSION;
+	}
+
+use_defaults:
+	major = sti_cpufreq_fetch_major();
+	if (major < 0) {
+		dev_err(dev, "Failed to obtain major version\n");
+		/* Use default major number */
+		major = DEFAULT_VERSION;
+	}
+
+	minor = sti_cpufreq_fetch_minor();
+	if (minor < 0) {
+		dev_err(dev, "Failed to obtain minor version\n");
+		/* Use default minor number */
+		minor = DEFAULT_VERSION;
+	}
+
+	snprintf(name, MAX_PCODE_NAME_LEN, "pcode%d", pcode);
+
+	ret = dev_pm_opp_set_prop_name(dev, name);
+	if (ret) {
+		dev_err(dev, "Failed to set prop name\n");
+		return ret;
+	}
+
+	version[0] = BIT(major);
+	version[1] = BIT(minor);
+	version[2] = BIT(substrate);
+
+	ret = dev_pm_opp_set_supported_hw(dev, version, VERSION_ELEMENTS);
+	if (ret) {
+		dev_err(dev, "Failed to set supported hardware\n");
+		return ret;
+	}
+
+	dev_dbg(dev, "pcode: %d major: %d minor: %d substrate: %d\n",
+		pcode, major, minor, substrate);
+	dev_dbg(dev, "version[0]: %x version[1]: %x version[2]: %x\n",
+		version[0], version[1], version[2]);
+
+	return 0;
+}
+
+static int sti_cpufreq_fetch_syscon_regsiters(void)
+{
+	struct device *dev = ddata.cpu;
+	struct device_node *np = dev->of_node;
+
+	ddata.syscfg = syscon_regmap_lookup_by_phandle(np, "st,syscfg");
+	if (IS_ERR(ddata.syscfg)) {
+		dev_err(dev,  "\"st,syscfg\" not supplied\n");
+		return PTR_ERR(ddata.syscfg);
+	}
+
+	ddata.syscfg_eng = syscon_regmap_lookup_by_phandle(np, "st,syscfg-eng");
+	if (IS_ERR(ddata.syscfg_eng)) {
+		dev_err(dev, "\"st,syscfg-eng\" not supplied\n");
+		return PTR_ERR(ddata.syscfg_eng);
+	}
+
+	return 0;
+}
+
+static int sti_cpufreq_init(void)
+{
+	int ret;
+
+	ddata.cpu = get_cpu_device(0);
+	if (!ddata.cpu) {
+		dev_err(ddata.cpu, "Failed to get device for CPU0\n");
+		goto skip_voltage_scaling;
+	}
+
+	if (!of_get_property(ddata.cpu->of_node, "operating-points-v2", NULL)) {
+		dev_err(ddata.cpu, "OPP-v2 not supported\n");
+		goto skip_voltage_scaling;
+	}
+
+	ret = sti_cpufreq_fetch_syscon_regsiters();
+	if (ret)
+		goto skip_voltage_scaling;
+
+	ret = sti_cpufreq_set_opp_info();
+	if (!ret)
+		goto register_cpufreq_dt;
+
+skip_voltage_scaling:
+	dev_err(ddata.cpu, "Not doing voltage scaling\n");
+
+register_cpufreq_dt:
+	platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
+
+	return 0;
+}
+module_init(sti_cpufreq_init);
+
+MODULE_DESCRIPTION("STMicroelectronics CPUFreq/OPP driver");
+MODULE_AUTHOR("Ajitpal Singh <ajitpal.singh@st.com>");
+MODULE_AUTHOR("Lee Jones <lee.jones@linaro.org>");
+MODULE_LICENSE("GPL v2");