cpufreq: ap806: add cpufreq driver for Armada 8K

Add cpufreq driver for Marvell AP-806 found on Aramda 8K.
The AP-806 has DFS (Dynamic Frequency Scaling) with coupled
clock domain for two clusters, so this driver will directly
use generic cpufreq-dt driver as backend.

Based on the work of Omri Itach <omrii@marvell.com>.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/Kconfig.arm

@@ -25,6 +25,17 @@ config ARM_ARMADA_37XX_CPUFREQ
 	  This adds the CPUFreq driver support for Marvell Armada 37xx SoCs.
 	  The Armada 37xx PMU supports 4 frequency and VDD levels.
 
+config ARM_ARMADA_8K_CPUFREQ
+	tristate "Armada 8K CPUFreq driver"
+	depends on ARCH_MVEBU && CPUFREQ_DT
+	help
+	  This enables the CPUFreq driver support for Marvell
+	  Armada8k SOCs.
+	  Armada8K device has the AP806 which supports scaling
+	  to any full integer divider.
+
+	  If in doubt, say N.
+
 # big LITTLE core layer and glue drivers
 config ARM_BIG_LITTLE_CPUFREQ
 	tristate "Generic ARM big LITTLE CPUfreq driver"

drivers/cpufreq/Makefile

@@ -50,6 +50,7 @@ obj-$(CONFIG_X86_SFI_CPUFREQ)		+= sfi-cpufreq.o
 obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ)	+= arm_big_little.o
 
 obj-$(CONFIG_ARM_ARMADA_37XX_CPUFREQ)	+= armada-37xx-cpufreq.o
+obj-$(CONFIG_ARM_ARMADA_8K_CPUFREQ)	+= armada-8k-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-8k-cpufreq.c

@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * CPUFreq support for Armada 8K
+ *
+ * Copyright (C) 2018 Marvell
+ *
+ * Omri Itach <omrii@marvell.com>
+ * Gregory Clement <gregory.clement@bootlin.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+
+/*
+ * Setup the opps list with the divider for the max frequency, that
+ * will be filled at runtime.
+ */
+static const int opps_div[] __initconst = {1, 2, 3, 4};
+
+static struct platform_device *armada_8k_pdev;
+
+struct freq_table {
+	struct device *cpu_dev;
+	unsigned int freq[ARRAY_SIZE(opps_div)];
+};
+
+/* If the CPUs share the same clock, then they are in the same cluster. */
+static void __init armada_8k_get_sharing_cpus(struct clk *cur_clk,
+					      struct cpumask *cpumask)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct device *cpu_dev;
+		struct clk *clk;
+
+		cpu_dev = get_cpu_device(cpu);
+		if (!cpu_dev) {
+			pr_warn("Failed to get cpu%d device\n", cpu);
+			continue;
+		}
+
+		clk = clk_get(cpu_dev, 0);
+		if (IS_ERR(clk)) {
+			pr_warn("Cannot get clock for CPU %d\n", cpu);
+		} else {
+			if (clk_is_match(clk, cur_clk))
+				cpumask_set_cpu(cpu, cpumask);
+
+			clk_put(clk);
+		}
+	}
+}
+
+static int __init armada_8k_add_opp(struct clk *clk, struct device *cpu_dev,
+				    struct freq_table *freq_tables,
+				    int opps_index)
+{
+	unsigned int cur_frequency;
+	unsigned int freq;
+	int i, ret;
+
+	/* Get nominal (current) CPU frequency. */
+	cur_frequency = clk_get_rate(clk);
+	if (!cur_frequency) {
+		dev_err(cpu_dev, "Failed to get clock rate for this CPU\n");
+		return -EINVAL;
+	}
+
+	freq_tables[opps_index].cpu_dev = cpu_dev;
+
+	for (i = 0; i < ARRAY_SIZE(opps_div); i++) {
+		freq = cur_frequency / opps_div[i];
+
+		ret = dev_pm_opp_add(cpu_dev, freq, 0);
+		if (ret)
+			return ret;
+
+		freq_tables[opps_index].freq[i] = freq;
+	}
+
+	return 0;
+}
+
+static void armada_8k_cpufreq_free_table(struct freq_table *freq_tables)
+{
+	int opps_index, nb_cpus = num_possible_cpus();
+
+	for (opps_index = 0 ; opps_index <= nb_cpus; opps_index++) {
+		int i;
+
+		/* If cpu_dev is NULL then we reached the end of the array */
+		if (!freq_tables[opps_index].cpu_dev)
+			break;
+
+		for (i = 0; i < ARRAY_SIZE(opps_div); i++) {
+			/*
+			 * A 0Hz frequency is not valid, this meant
+			 * that it was not yet initialized so there is
+			 * no more opp to free
+			 */
+			if (freq_tables[opps_index].freq[i] == 0)
+				break;
+
+			dev_pm_opp_remove(freq_tables[opps_index].cpu_dev,
+					  freq_tables[opps_index].freq[i]);
+		}
+	}
+
+	kfree(freq_tables);
+}
+
+static int __init armada_8k_cpufreq_init(void)
+{
+	int ret = 0, opps_index = 0, cpu, nb_cpus;
+	struct freq_table *freq_tables;
+	struct device_node *node;
+	struct cpumask cpus;
+
+	node = of_find_compatible_node(NULL, NULL, "marvell,ap806-cpu-clock");
+	if (!node || !of_device_is_available(node))
+		return -ENODEV;
+
+	nb_cpus = num_possible_cpus();
+	freq_tables = kcalloc(nb_cpus, sizeof(*freq_tables), GFP_KERNEL);
+	cpumask_copy(&cpus, cpu_possible_mask);
+
+	/*
+	 * For each CPU, this loop registers the operating points
+	 * supported (which are the nominal CPU frequency and full integer
+	 * divisions of it).
+	 */
+	for_each_cpu(cpu, &cpus) {
+		struct cpumask shared_cpus;
+		struct device *cpu_dev;
+		struct clk *clk;
+
+		cpu_dev = get_cpu_device(cpu);
+
+		if (!cpu_dev) {
+			pr_err("Cannot get CPU %d\n", cpu);
+			continue;
+		}
+
+		clk = clk_get(cpu_dev, 0);
+
+		if (IS_ERR(clk)) {
+			pr_err("Cannot get clock for CPU %d\n", cpu);
+			ret = PTR_ERR(clk);
+			goto remove_opp;
+		}
+
+		ret = armada_8k_add_opp(clk, cpu_dev, freq_tables, opps_index);
+		if (ret) {
+			clk_put(clk);
+			goto remove_opp;
+		}
+
+		opps_index++;
+		cpumask_clear(&shared_cpus);
+		armada_8k_get_sharing_cpus(clk, &shared_cpus);
+		dev_pm_opp_set_sharing_cpus(cpu_dev, &shared_cpus);
+		cpumask_andnot(&cpus, &cpus, &shared_cpus);
+		clk_put(clk);
+	}
+
+	armada_8k_pdev = platform_device_register_simple("cpufreq-dt", -1,
+							 NULL, 0);
+	ret = PTR_ERR_OR_ZERO(armada_8k_pdev);
+	if (ret)
+		goto remove_opp;
+
+	platform_set_drvdata(armada_8k_pdev, freq_tables);
+
+	return 0;
+
+remove_opp:
+	armada_8k_cpufreq_free_table(freq_tables);
+	return ret;
+}
+module_init(armada_8k_cpufreq_init);
+
+static void __exit armada_8k_cpufreq_exit(void)
+{
+	struct freq_table *freq_tables = platform_get_drvdata(armada_8k_pdev);
+
+	platform_device_unregister(armada_8k_pdev);
+	armada_8k_cpufreq_free_table(freq_tables);
+}
+module_exit(armada_8k_cpufreq_exit);
+
+MODULE_AUTHOR("Gregory Clement <gregory.clement@bootlin.com>");
+MODULE_DESCRIPTION("Armada 8K cpufreq driver");
+MODULE_LICENSE("GPL");