cpufreq: Add DVFS support for Armada 37xx

This patch adds DVFS support for the Armada 37xx SoCs

There are up to four CPU frequency loads for Armada 37xx controlled by
the hardware.

This driver associates the CPU load level to a frequency, then the
hardware will switch while selecting a load level.

The hardware also can associate a voltage for each level (AVS support)
but it is not yet supported

Tested-by: Andre Heider <a.heider@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.arm

@@ -18,6 +18,13 @@ config ACPI_CPPC_CPUFREQ
 
 	  If in doubt, say N.
 
+config ARM_ARMADA_37XX_CPUFREQ
+	tristate "Armada 37xx CPUFreq support"
+	depends on ARCH_MVEBU
+	help
+	  This adds the CPUFreq driver support for Marvell Armada 37xx SoCs.
+	  The Armada 37xx PMU supports 4 frequency and VDD levels.
+
 # big LITTLE core layer and glue drivers
 config ARM_BIG_LITTLE_CPUFREQ
 	tristate "Generic ARM big LITTLE CPUfreq driver"

drivers/cpufreq/Makefile

@@ -52,6 +52,7 @@ obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ)	+= arm_big_little.o
 # LITTLE drivers, so that it is probed last.
 obj-$(CONFIG_ARM_DT_BL_CPUFREQ)		+= arm_big_little_dt.o
 
+obj-$(CONFIG_ARM_ARMADA_37XX_CPUFREQ)	+= armada-37xx-cpufreq.o
 obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ)	+= brcmstb-avs-cpufreq.o
 obj-$(CONFIG_ACPI_CPPC_CPUFREQ)		+= cppc_cpufreq.o
 obj-$(CONFIG_ARCH_DAVINCI)		+= davinci-cpufreq.o

drivers/cpufreq/armada-37xx-cpufreq.c

@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * CPU frequency scaling support for Armada 37xx platform.
+ *
+ * Copyright (C) 2017 Marvell
+ *
+ * Gregory CLEMENT <gregory.clement@free-electrons.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/* Power management in North Bridge register set */
+#define ARMADA_37XX_NB_L0L1	0x18
+#define ARMADA_37XX_NB_L2L3	0x1C
+#define  ARMADA_37XX_NB_TBG_DIV_OFF	13
+#define  ARMADA_37XX_NB_TBG_DIV_MASK	0x7
+#define  ARMADA_37XX_NB_CLK_SEL_OFF	11
+#define  ARMADA_37XX_NB_CLK_SEL_MASK	0x1
+#define  ARMADA_37XX_NB_CLK_SEL_TBG	0x1
+#define  ARMADA_37XX_NB_TBG_SEL_OFF	9
+#define  ARMADA_37XX_NB_TBG_SEL_MASK	0x3
+#define  ARMADA_37XX_NB_VDD_SEL_OFF	6
+#define  ARMADA_37XX_NB_VDD_SEL_MASK	0x3
+#define  ARMADA_37XX_NB_CONFIG_SHIFT	16
+#define ARMADA_37XX_NB_DYN_MOD	0x24
+#define  ARMADA_37XX_NB_CLK_SEL_EN	BIT(26)
+#define  ARMADA_37XX_NB_TBG_EN		BIT(28)
+#define  ARMADA_37XX_NB_DIV_EN		BIT(29)
+#define  ARMADA_37XX_NB_VDD_EN		BIT(30)
+#define  ARMADA_37XX_NB_DFS_EN		BIT(31)
+#define ARMADA_37XX_NB_CPU_LOAD 0x30
+#define  ARMADA_37XX_NB_CPU_LOAD_MASK	0x3
+#define  ARMADA_37XX_DVFS_LOAD_0	0
+#define  ARMADA_37XX_DVFS_LOAD_1	1
+#define  ARMADA_37XX_DVFS_LOAD_2	2
+#define  ARMADA_37XX_DVFS_LOAD_3	3
+
+/*
+ * On Armada 37xx the Power management manages 4 level of CPU load,
+ * each level can be associated with a CPU clock source, a CPU
+ * divider, a VDD level, etc...
+ */
+#define LOAD_LEVEL_NR	4
+
+struct armada_37xx_dvfs {
+	u32 cpu_freq_max;
+	u8 divider[LOAD_LEVEL_NR];
+};
+
+static struct armada_37xx_dvfs armada_37xx_dvfs[] = {
+	{.cpu_freq_max = 1200*1000*1000, .divider = {1, 2, 4, 6} },
+	{.cpu_freq_max = 1000*1000*1000, .divider = {1, 2, 4, 5} },
+	{.cpu_freq_max = 800*1000*1000,  .divider = {1, 2, 3, 4} },
+	{.cpu_freq_max = 600*1000*1000,  .divider = {2, 4, 5, 6} },
+};
+
+static struct armada_37xx_dvfs *armada_37xx_cpu_freq_info_get(u32 freq)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(armada_37xx_dvfs); i++) {
+		if (freq == armada_37xx_dvfs[i].cpu_freq_max)
+			return &armada_37xx_dvfs[i];
+	}
+
+	pr_err("Unsupported CPU frequency %d MHz\n", freq/1000000);
+	return NULL;
+}
+
+/*
+ * Setup the four level managed by the hardware. Once the four level
+ * will be configured then the DVFS will be enabled.
+ */
+static void __init armada37xx_cpufreq_dvfs_setup(struct regmap *base,
+						 struct clk *clk, u8 *divider)
+{
+	int load_lvl;
+	struct clk *parent;
+
+	for (load_lvl = 0; load_lvl < LOAD_LEVEL_NR; load_lvl++) {
+		unsigned int reg, mask, val, offset = 0;
+
+		if (load_lvl <= ARMADA_37XX_DVFS_LOAD_1)
+			reg = ARMADA_37XX_NB_L0L1;
+		else
+			reg = ARMADA_37XX_NB_L2L3;
+
+		if (load_lvl == ARMADA_37XX_DVFS_LOAD_0 ||
+		    load_lvl == ARMADA_37XX_DVFS_LOAD_2)
+			offset += ARMADA_37XX_NB_CONFIG_SHIFT;
+
+		/* Set cpu clock source, for all the level we use TBG */
+		val = ARMADA_37XX_NB_CLK_SEL_TBG << ARMADA_37XX_NB_CLK_SEL_OFF;
+		mask = (ARMADA_37XX_NB_CLK_SEL_MASK
+			<< ARMADA_37XX_NB_CLK_SEL_OFF);
+
+		/*
+		 * Set cpu divider based on the pre-computed array in
+		 * order to have balanced step.
+		 */
+		val |= divider[load_lvl] << ARMADA_37XX_NB_TBG_DIV_OFF;
+		mask |= (ARMADA_37XX_NB_TBG_DIV_MASK
+			<< ARMADA_37XX_NB_TBG_DIV_OFF);
+
+		/* Set VDD divider which is actually the load level. */
+		val |= load_lvl << ARMADA_37XX_NB_VDD_SEL_OFF;
+		mask |= (ARMADA_37XX_NB_VDD_SEL_MASK
+			<< ARMADA_37XX_NB_VDD_SEL_OFF);
+
+		val <<= offset;
+		mask <<= offset;
+
+		regmap_update_bits(base, reg, mask, val);
+	}
+
+	/*
+	 * Set cpu clock source, for all the level we keep the same
+	 * clock source that the one already configured. For this one
+	 * we need to use the clock framework
+	 */
+	parent = clk_get_parent(clk);
+	clk_set_parent(clk, parent);
+}
+
+static void __init armada37xx_cpufreq_disable_dvfs(struct regmap *base)
+{
+	unsigned int reg = ARMADA_37XX_NB_DYN_MOD,
+		mask = ARMADA_37XX_NB_DFS_EN;
+
+	regmap_update_bits(base, reg, mask, 0);
+}
+
+static void __init armada37xx_cpufreq_enable_dvfs(struct regmap *base)
+{
+	unsigned int val, reg = ARMADA_37XX_NB_CPU_LOAD,
+		mask = ARMADA_37XX_NB_CPU_LOAD_MASK;
+
+	/* Start with the highest load (0) */
+	val = ARMADA_37XX_DVFS_LOAD_0;
+	regmap_update_bits(base, reg, mask, val);
+
+	/* Now enable DVFS for the CPUs */
+	reg = ARMADA_37XX_NB_DYN_MOD;
+	mask =	ARMADA_37XX_NB_CLK_SEL_EN | ARMADA_37XX_NB_TBG_EN |
+		ARMADA_37XX_NB_DIV_EN | ARMADA_37XX_NB_VDD_EN |
+		ARMADA_37XX_NB_DFS_EN;
+
+	regmap_update_bits(base, reg, mask, mask);
+}
+
+static int __init armada37xx_cpufreq_driver_init(void)
+{
+	struct armada_37xx_dvfs *dvfs;
+	struct platform_device *pdev;
+	unsigned int cur_frequency;
+	struct regmap *nb_pm_base;
+	struct device *cpu_dev;
+	int load_lvl, ret;
+	struct clk *clk;
+
+	nb_pm_base =
+		syscon_regmap_lookup_by_compatible("marvell,armada-3700-nb-pm");
+
+	if (IS_ERR(nb_pm_base))
+		return -ENODEV;
+
+	/* Before doing any configuration on the DVFS first, disable it */
+	armada37xx_cpufreq_disable_dvfs(nb_pm_base);
+
+	/*
+	 * On CPU 0 register the operating points supported (which are
+	 * the nominal CPU frequency and full integer divisions of
+	 * it).
+	 */
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev) {
+		dev_err(cpu_dev, "Cannot get CPU\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);
+	}
+
+	/* Get nominal (current) CPU frequency */
+	cur_frequency = clk_get_rate(clk);
+	if (!cur_frequency) {
+		dev_err(cpu_dev, "Failed to get clock rate for CPU\n");
+		return -EINVAL;
+	}
+
+	dvfs = armada_37xx_cpu_freq_info_get(cur_frequency);
+	if (!dvfs)
+		return -EINVAL;
+
+	armada37xx_cpufreq_dvfs_setup(nb_pm_base, clk, dvfs->divider);
+
+	for (load_lvl = ARMADA_37XX_DVFS_LOAD_0; load_lvl < LOAD_LEVEL_NR;
+	     load_lvl++) {
+		unsigned long freq = cur_frequency / dvfs->divider[load_lvl];
+
+		ret = dev_pm_opp_add(cpu_dev, freq, 0);
+		if (ret) {
+			/* clean-up the already added opp before leaving */
+			while (load_lvl-- > ARMADA_37XX_DVFS_LOAD_0) {
+				freq = cur_frequency / dvfs->divider[load_lvl];
+				dev_pm_opp_remove(cpu_dev, freq);
+			}
+			return ret;
+		}
+	}
+
+	/* Now that everything is setup, enable the DVFS at hardware level */
+	armada37xx_cpufreq_enable_dvfs(nb_pm_base);
+
+	pdev = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
+
+	return PTR_ERR_OR_ZERO(pdev);
+}
+/* late_initcall, to guarantee the driver is loaded after A37xx clock driver */
+late_initcall(armada37xx_cpufreq_driver_init);
+
+MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@free-electrons.com>");
+MODULE_DESCRIPTION("Armada 37xx cpufreq driver");
+MODULE_LICENSE("GPL");