[PATCH 2/2] cpufreq: add cpufreq driver for Mediatek MT8173 SoC

[pi-cheng.chen]

When doing DVFS on MT8173 SoC, 2 rules should be followed to make sure the
SoC works properly:
1. When doing frequency scaling of CPUs, the clock source should be switched
   to another PLL, then switched back to the orignal until it's stable.
2. When doing voltage scaling of CA57 cluster, Vproc and Vsram need to be
   controlled concurrently and 2 limitations should be followed:
   a. Vsram > Vproc
   b. Vsram - Vproc < 200 mV

To address these needs, we reuse cpufreq-dt but do voltage scaling in the
cpufreq notifier.

Signed-off-by: pi-cheng.chen <pi-cheng.chen@xxxxxxxxxx>
---
 drivers/cpufreq/Kconfig.arm      |   6 +
 drivers/cpufreq/Makefile         |   1 +
 drivers/cpufreq/mt8173-cpufreq.c | 459 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 466 insertions(+)
 create mode 100644 drivers/cpufreq/mt8173-cpufreq.c

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 0f9a2c3..97ed7dd 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -255,3 +255,9 @@ config ARM_PXA2xx_CPUFREQ
 	  This add the CPUFreq driver support for Intel PXA2xx SOCs.
 
 	  If in doubt, say N.
+
+config ARM_MT8173_CPUFREQ
+	bool "Mediatek MT8173 CPUFreq support"
+	depends on ARCH_MEDIATEK && CPUFREQ_DT && REGULATOR
+	help
+	  This adds the CPUFreq driver support for Mediatek MT8173 SoC.
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index b3ca7b0..67b7f17 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_ARM_SA1110_CPUFREQ)	+= sa1110-cpufreq.o
 obj-$(CONFIG_ARM_SPEAR_CPUFREQ)		+= spear-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA_CPUFREQ)		+= tegra-cpufreq.o
 obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ)	+= vexpress-spc-cpufreq.o
+obj-$(CONFIG_ARM_MT8173_CPUFREQ)	+= mt8173-cpufreq.o
 
 ##################################################################################
 # PowerPC platform drivers
diff --git a/drivers/cpufreq/mt8173-cpufreq.c b/drivers/cpufreq/mt8173-cpufreq.c
new file mode 100644
index 0000000..b578c10
--- /dev/null
+++ b/drivers/cpufreq/mt8173-cpufreq.c
@@ -0,0 +1,459 @@
+/*
+* Copyright (c) 2015 Linaro.
+* Author: Pi-Cheng Chen <pi-cheng.chen@xxxxxxxxxx>
+*
+* This program is free software; you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*/
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/cpufreq.h>
+#include <linux/cpufreq-dt.h>
+#include <linux/cpumask.h>
+#include <linux/slab.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/regulator/consumer.h>
+#include <linux/cpu.h>
+#include <linux/pm_opp.h>
+
+#define CPUCLK_MUX_ARMPLL	0x1
+#define CPUCLK_MUX_MAINPLL	0x2
+#define VOLT_SHIFT_LIMIT	150000
+
+enum {
+	LITTLE_CLUSTER = 0,
+	BIG_CLUSTER,
+	NR_CLUSTERS
+};
+
+static struct cluster_dvfs_info {
+	int cpu;
+	struct cpumask cpus;
+	struct device *cpu_dev;
+	struct regulator *proc_reg;
+	struct regulator *sram_reg;
+	int inter_volt;
+	u32 volt_tol;
+} *dvfs_info;
+
+static unsigned long mainpll_freq;
+static void __iomem *clk_mux_regs;
+static spinlock_t lock;
+
+static void cpuclk_mux_set(int cluster, u32 sel)
+{
+	u32 val;
+	u32 mask = 0x3;
+
+	if (cluster == BIG_CLUSTER) {
+		mask <<= 2;
+		sel <<= 2;
+	}
+
+	spin_lock(&lock);
+
+	val = readl(clk_mux_regs);
+	val = (val & ~mask) | sel;
+	writel(val, clk_mux_regs);
+
+	spin_unlock(&lock);
+}
+
+static int mt8173_cpufreq_voltage_step(struct cluster_dvfs_info *dvfs,
+				       unsigned long old_vproc,
+				       unsigned long new_vproc)
+{
+	int cur_vsram, cur_vproc, target_volt, tol;
+
+	if (old_vproc > new_vproc) {
+		while (1) {
+			cur_vsram = regulator_get_voltage(dvfs->sram_reg);
+			if (cur_vsram - new_vproc < VOLT_SHIFT_LIMIT &&
+			    cur_vsram > new_vproc) {
+				tol = new_vproc * dvfs->volt_tol / 100;
+				regulator_set_voltage_tol(dvfs->proc_reg,
+							  new_vproc, tol);
+				break;
+			}
+
+			target_volt = cur_vsram - VOLT_SHIFT_LIMIT;
+			tol = target_volt * dvfs->volt_tol / 100;
+			regulator_set_voltage_tol(dvfs->proc_reg, target_volt,
+						  tol);
+
+			cur_vproc = regulator_get_voltage(dvfs->proc_reg);
+			target_volt = cur_vproc + 1;
+			tol = target_volt * dvfs->volt_tol / 100;
+			regulator_set_voltage_tol(dvfs->sram_reg, target_volt,
+						  tol);
+		}
+	} else if (old_vproc < new_vproc) {
+		while (1) {
+			cur_vsram = regulator_get_voltage(dvfs->sram_reg);
+			if (cur_vsram - new_vproc < VOLT_SHIFT_LIMIT &&
+			    cur_vsram > new_vproc) {
+				tol = new_vproc * dvfs->volt_tol / 100;
+				regulator_set_voltage_tol(dvfs->proc_reg,
+							  new_vproc, tol);
+				break;
+			}
+
+			cur_vproc = regulator_get_voltage(dvfs->proc_reg);
+			target_volt = cur_vproc + VOLT_SHIFT_LIMIT;
+			tol = target_volt * dvfs->volt_tol / 100;
+			regulator_set_voltage_tol(dvfs->sram_reg, target_volt,
+						  tol);
+
+			if (new_vproc - cur_vproc > VOLT_SHIFT_LIMIT) {
+				cur_vsram = regulator_get_voltage(
+							dvfs->sram_reg);
+				target_volt = cur_vsram - 1;
+				tol = target_volt * dvfs->volt_tol / 100;
+				regulator_set_voltage_tol(dvfs->proc_reg,
+							  target_volt, tol);
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int get_opp_voltage(struct device *dev, unsigned long freq_hz)
+{
+	struct dev_pm_opp *opp;
+	int volt;
+
+	rcu_read_lock();
+	opp = dev_pm_opp_find_freq_ceil(dev, &freq_hz);
+	if (IS_ERR(opp)) {
+		rcu_read_unlock();
+		pr_err("%s: failed to find OPP for %lu\n", __func__, freq_hz);
+		return PTR_ERR(opp);
+	}
+	volt = dev_pm_opp_get_voltage(opp);
+	rcu_read_unlock();
+
+	return volt;
+}
+
+static int mt8173_cpufreq_get_intermediate_voltage(int cluster)
+{
+	struct cluster_dvfs_info *dvfs = &dvfs_info[cluster];
+
+	if (dvfs->inter_volt == 0)
+		dvfs->inter_volt = get_opp_voltage(dvfs->cpu_dev,
+						   mainpll_freq);
+
+	return dvfs->inter_volt;
+}
+
+static void mt8173_cpufreq_set_voltage(int cluster, int old_volt, int new_volt)
+{
+	struct cluster_dvfs_info *dvfs = &dvfs_info[cluster];
+	int ret = 0;
+
+	if (cluster == LITTLE_CLUSTER) {
+		int tol;
+
+		tol = new_volt * dvfs->volt_tol / 100;
+		ret = regulator_set_voltage_tol(dvfs->proc_reg, new_volt, tol);
+	} else {
+		ret = mt8173_cpufreq_voltage_step(dvfs, old_volt, new_volt);
+	}
+
+	if (ret)
+		pr_err("%s: cluster%d failed to scale voltage (%dmV to %dmV)",
+		       __func__, cluster, old_volt, new_volt);
+}
+
+static int mt8173_cpufreq_notify(struct notifier_block *nb,
+				 unsigned long action, void *data)
+{
+	struct cpufreq_freqs *freqs = data;
+	struct cluster_dvfs_info *dvfs;
+	unsigned long old_volt, new_volt, inter_volt;
+	int cluster;
+
+	if (freqs->cpu == dvfs_info[BIG_CLUSTER].cpu)
+		cluster = BIG_CLUSTER;
+	else if (freqs->cpu == dvfs_info[LITTLE_CLUSTER].cpu)
+		cluster = LITTLE_CLUSTER;
+	else
+		return NOTIFY_DONE;
+
+	dvfs = &dvfs_info[cluster];
+
+	old_volt = regulator_get_voltage(dvfs->proc_reg);
+
+	new_volt = get_opp_voltage(dvfs->cpu_dev, freqs->new * 1000);
+	inter_volt = mt8173_cpufreq_get_intermediate_voltage(cluster);
+
+	if (action == CPUFREQ_PRECHANGE) {
+		if (old_volt < inter_volt || old_volt < new_volt) {
+			new_volt = inter_volt > new_volt ?
+				   inter_volt : new_volt;
+			mt8173_cpufreq_set_voltage(cluster, old_volt,
+						   new_volt);
+		}
+
+		cpuclk_mux_set(cluster, CPUCLK_MUX_MAINPLL);
+	} else if (action == CPUFREQ_POSTCHANGE) {
+		cpuclk_mux_set(cluster, CPUCLK_MUX_ARMPLL);
+
+		if (new_volt < old_volt)
+			mt8173_cpufreq_set_voltage(cluster, old_volt,
+						   new_volt);
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block mt8173_cpufreq_nb = {
+	.notifier_call = mt8173_cpufreq_notify,
+};
+
+static struct cpufreq_dt_platform_data *pd;
+
+static int cpu_in_domain_list(struct list_head *domain_list, int cpu)
+{
+	struct list_head *node;
+
+	list_for_each(node, domain_list) {
+		struct cpufreq_cpu_domain *domain;
+
+		domain = container_of(node, struct cpufreq_cpu_domain, node);
+		if (cpumask_test_cpu(cpu, &domain->cpus))
+			return 1;
+	}
+
+	return 0;
+}
+
+static void cpufreq_dt_pdata_release(void)
+{
+	if (!pd)
+		return;
+
+	if (!list_empty(&pd->domain_list)) {
+		struct list_head *node, *tmp;
+		struct cpufreq_cpu_domain *domain;
+
+		list_for_each_safe(node, tmp, &pd->domain_list) {
+			list_del(node);
+			domain = container_of(node, struct cpufreq_cpu_domain,
+					      node);
+			kfree(domain);
+		}
+	}
+
+	kfree(pd);
+}
+
+static int cpufreq_dt_pdata_init(void)
+{
+	int cpu;
+
+	pd = kmalloc(sizeof(*pd), GFP_KERNEL);
+	if (!pd)
+		return -ENOMEM;
+
+	pd->independent_clocks = 1,
+	INIT_LIST_HEAD(&pd->domain_list);
+
+	for_each_possible_cpu(cpu) {
+		struct cpufreq_cpu_domain *new_domain;
+
+		if (cpu_in_domain_list(&pd->domain_list, cpu))
+			continue;
+
+		new_domain = kzalloc(sizeof(*new_domain), GFP_KERNEL);
+		if (!new_domain) {
+			cpufreq_dt_pdata_release();
+			return -ENOMEM;
+		}
+
+		cpumask_copy(&new_domain->cpus,
+			     &cpu_topology[cpu].core_sibling);
+		list_add(&new_domain->node, &pd->domain_list);
+	}
+
+	return 0;
+}
+
+static void mt8173_cpufreq_dvfs_info_release(void)
+{
+	int i;
+
+	if (!dvfs_info)
+		return;
+
+	for (i = 0; i < NR_CLUSTERS; ++i) {
+		struct cluster_dvfs_info *dvfs = &dvfs_info[i];
+
+		if (!IS_ERR_OR_NULL(dvfs->proc_reg))
+			regulator_put(dvfs->proc_reg);
+
+		if (!IS_ERR_OR_NULL(dvfs->sram_reg))
+			regulator_put(dvfs->sram_reg);
+	}
+
+	if (clk_mux_regs)
+		iounmap(clk_mux_regs);
+}
+
+static int mt8173_cpufreq_dvfs_info_init(void)
+{
+	struct list_head *node;
+	struct device_node *np;
+	struct clk *mainpll;
+	int i, ret;
+
+	dvfs_info = kzalloc(sizeof(*dvfs) * NR_CLUSTERS, GFP_KERNEL);
+	if (!dvfs_info)
+		return -ENOMEM;
+
+	list_for_each(node, &pd->domain_list) {
+		struct cpufreq_cpu_domain *domain = container_of(
+					node, struct cpufreq_cpu_domain, node);
+		int cpu = cpumask_next(0, &domain->cpus);
+
+		np = of_get_cpu_node(cpu, NULL);
+
+		if (of_property_match_string(np, "compatible",
+					     "arm,cortex-a53") >= 0)
+			cpumask_copy(&dvfs_info[LITTLE_CLUSTER].cpus,
+				     &domain->cpus);
+		else if (of_property_match_string(np, "compatible",
+						  "arm,cortex-a57") >= 0)
+			cpumask_copy(&dvfs_info[BIG_CLUSTER].cpus,
+				     &domain->cpus);
+		else {
+			of_node_put(np);
+			pr_err("%s: unknown CPU core\n", __func__);
+			return -EINVAL;
+		}
+
+		of_node_put(np);
+	}
+
+	for (i = 0; i < NR_CLUSTERS; i++) {
+		struct cluster_dvfs_info *dvfs = &dvfs_info[i];
+		int cpu;
+
+		for_each_cpu_mask(cpu, dvfs->cpus) {
+			struct device_node *np;
+
+			dvfs->cpu_dev = get_cpu_device(cpu);
+			dvfs->proc_reg = regulator_get(dvfs->cpu_dev, "proc");
+			if (IS_ERR(dvfs->proc_reg))
+				continue;
+
+			dvfs->cpu = cpu;
+			dvfs->sram_reg = regulator_get(dvfs->cpu_dev, "sram");
+
+			np = of_node_get(dvfs->cpu_dev->of_node);
+			of_property_read_u32(np, "voltage-tolerance",
+					     &dvfs->volt_tol);
+			of_node_put(np);
+			break;
+		}
+
+		if (IS_ERR(dvfs->proc_reg)) {
+			pr_err("%s: no proc regulator for cluster %d\n",
+			       __func__, i);
+			ret = -ENODEV;
+			goto dvfs_info_release;
+		}
+
+		if (IS_ERR(dvfs->sram_reg) && BIG_CLUSTER == i) {
+			pr_err("%s: no sram regulator for cluster %d\n",
+			       __func__, i);
+			ret = -ENODEV;
+			goto dvfs_info_release;
+		}
+	}
+
+	mainpll = __clk_lookup("mainpll");
+	if (!mainpll) {
+		pr_err("failed to get mainpll clk\n");
+		ret = -ENOENT;
+		goto dvfs_info_release;
+	}
+	mainpll_freq = clk_get_rate(mainpll);
+
+	np = of_find_compatible_node(NULL, NULL, "mediatek,mt8173-infrasys");
+	if (!np) {
+		pr_err("failed to find clock mux registers\n");
+		ret = -ENODEV;
+		goto dvfs_info_release;
+	}
+
+	clk_mux_regs = of_iomap(np, 0);
+	if (!clk_mux_regs) {
+		pr_err("failed to map clock mux registers\n");
+		ret = -EFAULT;
+		goto dvfs_info_release;
+	}
+	of_node_put(np);
+
+	spin_lock_init(&lock);
+
+	return 0;
+
+dvfs_info_release:
+	mt8173_cpufreq_dvfs_info_release();
+	return ret;
+}
+
+static int mt8173_cpufreq_driver_init(void)
+{
+	int ret;
+
+	if (!of_machine_is_compatible("mediatek,mt8173"))
+		return -ENODEV;
+
+	ret = cpufreq_dt_pdata_init();
+	if (ret) {
+		pr_err("failed to initialize platform data: %d\n", ret);
+		return ret;
+	}
+
+	ret = mt8173_cpufreq_dvfs_info_init();
+	if (ret) {
+		pr_err("failed to initialize mt8173 dvfs info: %d\n", ret);
+		goto dt_pdata_release;
+	}
+
+	ret = cpufreq_register_notifier(&mt8173_cpufreq_nb,
+					CPUFREQ_TRANSITION_NOTIFIER);
+	if (ret) {
+		pr_err("failed to register cpufreq notifier: %d\n", ret);
+		goto dt_pdata_release;
+	}
+
+	platform_device_register_data(NULL, "cpufreq-dt", -1,
+				      pd, sizeof(*pd));
+
+	return 0;
+
+dt_pdata_release:
+	cpufreq_dt_pdata_release();
+	return ret;
+}
+
+module_init(mt8173_cpufreq_driver_init);
+
+MODULE_AUTHOR("Pi-Cheng Chen <pi-cheng.chen@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Mediatek MT8173 cpufreq driver");
+MODULE_LICENSE("GPL");
+
-- 
1.9.1

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