soc: samsung: Add Exynos Adaptive Supply Voltage driver

The Adaptive Supply Voltage (ASV) driver adjusts CPU cluster operating
points depending on exact revision of an SoC retrieved from the CHIPID
block or the OTP memory.  This allows for some power saving as for some
CPU clock frequencies we can lower CPU cluster's supply voltage comparing
to safe values common to all the SoC revisions.

This patch adds support for Exynos5422/5800 SoC, it is partially based
on code from https://github.com/hardkernel/linux repository,
branch odroidxu4-4.14.y, files: arch/arm/mach-exynos/exynos5422-asv.[ch].

Tested on Odroid XU3, XU4, XU3 Lite.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

drivers/soc/samsung/Kconfig

@@ -7,6 +7,16 @@ menuconfig SOC_SAMSUNG
 
 if SOC_SAMSUNG
 
+config EXYNOS_ASV
+	bool "Exynos Adaptive Supply Voltage support" if COMPILE_TEST
+	depends on (ARCH_EXYNOS && EXYNOS_CHIPID) || COMPILE_TEST
+	select EXYNOS_ASV_ARM if ARM && ARCH_EXYNOS
+
+# There is no need to enable these drivers for ARMv8
+config EXYNOS_ASV_ARM
+	bool "Exynos ASV ARMv7-specific driver extensions" if COMPILE_TEST
+	depends on EXYNOS_ASV
+
 config EXYNOS_CHIPID
 	bool "Exynos Chipid controller driver" if COMPILE_TEST
 	depends on ARCH_EXYNOS || COMPILE_TEST

drivers/soc/samsung/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
+obj-$(CONFIG_EXYNOS_ASV)	+= exynos-asv.o
+obj-$(CONFIG_EXYNOS_ASV_ARM)	+= exynos5422-asv.o
+
 obj-$(CONFIG_EXYNOS_CHIPID)	+= exynos-chipid.o
 obj-$(CONFIG_EXYNOS_PMU)	+= exynos-pmu.o
 

drivers/soc/samsung/exynos-asv.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019 Samsung Electronics Co., Ltd.
+ *	      http://www.samsung.com/
+ * Author: Sylwester Nawrocki <s.nawrocki@samsung.com>
+ *
+ * Samsung Exynos SoC Adaptive Supply Voltage support
+ */
+
+#include <linux/cpu.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/regmap.h>
+#include <linux/soc/samsung/exynos-chipid.h>
+
+#include "exynos-asv.h"
+#include "exynos5422-asv.h"
+
+#define MHZ 1000000U
+
+static int exynos_asv_update_cpu_opps(struct exynos_asv *asv,
+				      struct device *cpu)
+{
+	struct exynos_asv_subsys *subsys = NULL;
+	struct dev_pm_opp *opp;
+	unsigned int opp_freq;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(asv->subsys); i++) {
+		if (of_device_is_compatible(cpu->of_node,
+					    asv->subsys[i].cpu_dt_compat)) {
+			subsys = &asv->subsys[i];
+			break;
+		}
+	}
+	if (!subsys)
+		return -EINVAL;
+
+	for (i = 0; i < subsys->table.num_rows; i++) {
+		unsigned int new_volt, volt;
+		int ret;
+
+		opp_freq = exynos_asv_opp_get_frequency(subsys, i);
+
+		opp = dev_pm_opp_find_freq_exact(cpu, opp_freq * MHZ, true);
+		if (IS_ERR(opp)) {
+			dev_info(asv->dev, "cpu%d opp%d, freq: %u missing\n",
+				 cpu->id, i, opp_freq);
+
+			continue;
+		}
+
+		volt = dev_pm_opp_get_voltage(opp);
+		new_volt = asv->opp_get_voltage(subsys, i, volt);
+		dev_pm_opp_put(opp);
+
+		if (new_volt == volt)
+			continue;
+
+		ret = dev_pm_opp_adjust_voltage(cpu, opp_freq * MHZ,
+						new_volt, new_volt, new_volt);
+		if (ret < 0)
+			dev_err(asv->dev,
+				"Failed to adjust OPP %u Hz/%u uV for cpu%d\n",
+				opp_freq, new_volt, cpu->id);
+		else
+			dev_dbg(asv->dev,
+				"Adjusted OPP %u Hz/%u -> %u uV, cpu%d\n",
+				opp_freq, volt, new_volt, cpu->id);
+	}
+
+	return 0;
+}
+
+static int exynos_asv_update_opps(struct exynos_asv *asv)
+{
+	struct opp_table *last_opp_table = NULL;
+	struct device *cpu;
+	int ret, cpuid;
+
+	for_each_possible_cpu(cpuid) {
+		struct opp_table *opp_table;
+
+		cpu = get_cpu_device(cpuid);
+		if (!cpu)
+			continue;
+
+		opp_table = dev_pm_opp_get_opp_table(cpu);
+		if (IS_ERR(opp_table))
+			continue;
+
+		if (!last_opp_table || opp_table != last_opp_table) {
+			last_opp_table = opp_table;
+
+			ret = exynos_asv_update_cpu_opps(asv, cpu);
+			if (ret < 0)
+				dev_err(asv->dev, "Couldn't udate OPPs for cpu%d\n",
+					cpuid);
+		}
+
+		dev_pm_opp_put_opp_table(opp_table);
+	}
+
+	return	0;
+}
+
+static int exynos_asv_probe(struct platform_device *pdev)
+{
+	int (*probe_func)(struct exynos_asv *asv);
+	struct exynos_asv *asv;
+	struct device *cpu_dev;
+	u32 product_id = 0;
+	int ret, i;
+
+	cpu_dev = get_cpu_device(0);
+	ret = dev_pm_opp_get_opp_count(cpu_dev);
+	if (ret < 0)
+		return -EPROBE_DEFER;
+
+	asv = devm_kzalloc(&pdev->dev, sizeof(*asv), GFP_KERNEL);
+	if (!asv)
+		return -ENOMEM;
+
+	asv->chipid_regmap = device_node_to_regmap(pdev->dev.of_node);
+	if (IS_ERR(asv->chipid_regmap)) {
+		dev_err(&pdev->dev, "Could not find syscon regmap\n");
+		return PTR_ERR(asv->chipid_regmap);
+	}
+
+	regmap_read(asv->chipid_regmap, EXYNOS_CHIPID_REG_PRO_ID, &product_id);
+
+	switch (product_id & EXYNOS_MASK) {
+	case 0xE5422000:
+		probe_func = exynos5422_asv_init;
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	ret = of_property_read_u32(pdev->dev.of_node, "samsung,asv-bin",
+				   &asv->of_bin);
+	if (ret < 0)
+		asv->of_bin = -EINVAL;
+
+	asv->dev = &pdev->dev;
+	dev_set_drvdata(&pdev->dev, asv);
+
+	for (i = 0; i < ARRAY_SIZE(asv->subsys); i++)
+		asv->subsys[i].asv = asv;
+
+	ret = probe_func(asv);
+	if (ret < 0)
+		return ret;
+
+	return exynos_asv_update_opps(asv);
+}
+
+static const struct of_device_id exynos_asv_of_device_ids[] = {
+	{ .compatible = "samsung,exynos4210-chipid" },
+	{}
+};
+
+static struct platform_driver exynos_asv_driver = {
+	.driver = {
+		.name = "exynos-asv",
+		.of_match_table = exynos_asv_of_device_ids,
+	},
+	.probe	= exynos_asv_probe,
+};
+module_platform_driver(exynos_asv_driver);

drivers/soc/samsung/exynos-asv.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2019 Samsung Electronics Co., Ltd.
+ *	      http://www.samsung.com/
+ * Author: Sylwester Nawrocki <s.nawrocki@samsung.com>
+ *
+ * Samsung Exynos SoC Adaptive Supply Voltage support
+ */
+#ifndef __LINUX_SOC_EXYNOS_ASV_H
+#define __LINUX_SOC_EXYNOS_ASV_H
+
+struct regmap;
+
+/* HPM, IDS values to select target group */
+struct asv_limit_entry {
+	unsigned int hpm;
+	unsigned int ids;
+};
+
+struct exynos_asv_table {
+	unsigned int num_rows;
+	unsigned int num_cols;
+	u32 *buf;
+};
+
+struct exynos_asv_subsys {
+	struct exynos_asv *asv;
+	const char *cpu_dt_compat;
+	int id;
+	struct exynos_asv_table table;
+
+	unsigned int base_volt;
+	unsigned int offset_volt_h;
+	unsigned int offset_volt_l;
+};
+
+struct exynos_asv {
+	struct device *dev;
+	struct regmap *chipid_regmap;
+	struct exynos_asv_subsys subsys[2];
+
+	int (*opp_get_voltage)(const struct exynos_asv_subsys *subs,
+			       int level, unsigned int voltage);
+	unsigned int group;
+	unsigned int table;
+
+	/* True if SG fields from PKG_ID register should be used */
+	bool use_sg;
+	/* ASV bin read from DT */
+	int of_bin;
+};
+
+static inline u32 __asv_get_table_entry(const struct exynos_asv_table *table,
+					unsigned int row, unsigned int col)
+{
+	return table->buf[row * (table->num_cols) + col];
+}
+
+static inline u32 exynos_asv_opp_get_voltage(const struct exynos_asv_subsys *subsys,
+					unsigned int level, unsigned int group)
+{
+	return __asv_get_table_entry(&subsys->table, level, group + 1);
+}
+
+static inline u32 exynos_asv_opp_get_frequency(const struct exynos_asv_subsys *subsys,
+					unsigned int level)
+{
+	return __asv_get_table_entry(&subsys->table, level, 0);
+}
+
+#endif /* __LINUX_SOC_EXYNOS_ASV_H */

drivers/soc/samsung/exynos5422-asv.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2019 Samsung Electronics Co., Ltd.
+ *	      http://www.samsung.com/
+ *
+ * Samsung Exynos 5422 SoC Adaptive Supply Voltage support
+ */
+
+#ifndef __LINUX_SOC_EXYNOS5422_ASV_H
+#define __LINUX_SOC_EXYNOS5422_ASV_H
+
+#include <linux/errno.h>
+
+enum {
+	EXYNOS_ASV_SUBSYS_ID_ARM,
+	EXYNOS_ASV_SUBSYS_ID_KFC,
+	EXYNOS_ASV_SUBSYS_ID_MAX
+};
+
+struct exynos_asv;
+
+#ifdef CONFIG_EXYNOS_ASV_ARM
+int exynos5422_asv_init(struct exynos_asv *asv);
+#else
+static inline int exynos5422_asv_init(struct exynos_asv *asv)
+{
+	return -ENOTSUPP;
+}
+#endif
+
+#endif /* __LINUX_SOC_EXYNOS5422_ASV_H */