cpufreq: airoha: Add EN7581 CPUFreq SMCCC driver

Add simple CPU Freq driver for Airoha EN7581 SoC that control CPU
frequency scaling with SMC APIs and register a generic "cpufreq-dt"
device.

All CPU share the same frequency and can't be controlled independently.
CPU frequency is controlled by the attached PM domain.

Add SoC compatible to cpufreq-dt-plat block list as a dedicated cpufreq
driver is needed with OPP v2 nodes declared in DTS.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/Kconfig.arm

@@ -15,6 +15,14 @@ config ARM_ALLWINNER_SUN50I_CPUFREQ_NVMEM
 	  To compile this driver as a module, choose M here: the
 	  module will be called sun50i-cpufreq-nvmem.
 
+config ARM_AIROHA_SOC_CPUFREQ
+	tristate "Airoha EN7581 SoC CPUFreq support"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	select PM_OPP
+	default ARCH_AIROHA
+	help
+	  This adds the CPUFreq driver for Airoha EN7581 SoCs.
+
 config ARM_APPLE_SOC_CPUFREQ
 	tristate "Apple Silicon SoC CPUFreq support"
 	depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)

drivers/cpufreq/Makefile

@@ -53,6 +53,7 @@ obj-$(CONFIG_X86_AMD_FREQ_SENSITIVITY)	+= amd_freq_sensitivity.o
 
 ##################################################################################
 # ARM SoC drivers
+obj-$(CONFIG_ARM_AIROHA_SOC_CPUFREQ)	+= airoha-cpufreq.o
 obj-$(CONFIG_ARM_APPLE_SOC_CPUFREQ)	+= apple-soc-cpufreq.o
 obj-$(CONFIG_ARM_ARMADA_37XX_CPUFREQ)	+= armada-37xx-cpufreq.o
 obj-$(CONFIG_ARM_ARMADA_8K_CPUFREQ)	+= armada-8k-cpufreq.o

drivers/cpufreq/airoha-cpufreq.c

@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bitfield.h>
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+
+#include "cpufreq-dt.h"
+
+struct airoha_cpufreq_priv {
+	int opp_token;
+	struct dev_pm_domain_list *pd_list;
+	struct platform_device *cpufreq_dt;
+};
+
+static struct platform_device *cpufreq_pdev;
+
+/* NOP function to disable OPP from setting clock */
+static int airoha_cpufreq_config_clks_nop(struct device *dev,
+					  struct opp_table *opp_table,
+					  struct dev_pm_opp *opp,
+					  void *data, bool scaling_down)
+{
+	return 0;
+}
+
+static const char * const airoha_cpufreq_clk_names[] = { "cpu", NULL };
+static const char * const airoha_cpufreq_pd_names[] = { "perf" };
+
+static int airoha_cpufreq_probe(struct platform_device *pdev)
+{
+	const struct dev_pm_domain_attach_data attach_data = {
+		.pd_names = airoha_cpufreq_pd_names,
+		.num_pd_names = ARRAY_SIZE(airoha_cpufreq_pd_names),
+		.pd_flags = PD_FLAG_DEV_LINK_ON | PD_FLAG_REQUIRED_OPP,
+	};
+	struct dev_pm_opp_config config = {
+		.clk_names = airoha_cpufreq_clk_names,
+		.config_clks = airoha_cpufreq_config_clks_nop,
+	};
+	struct platform_device *cpufreq_dt;
+	struct airoha_cpufreq_priv *priv;
+	struct device *dev = &pdev->dev;
+	struct device *cpu_dev;
+	int ret;
+
+	/* CPUs refer to the same OPP table */
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev)
+		return -ENODEV;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	/* Set OPP table conf with NOP config_clks */
+	priv->opp_token = dev_pm_opp_set_config(cpu_dev, &config);
+	if (priv->opp_token < 0)
+		return dev_err_probe(dev, priv->opp_token, "Failed to set OPP config\n");
+
+	/* Attach PM for OPP */
+	ret = dev_pm_domain_attach_list(cpu_dev, &attach_data,
+					&priv->pd_list);
+	if (ret)
+		goto clear_opp_config;
+
+	cpufreq_dt = platform_device_register_simple("cpufreq-dt", -1, NULL, 0);
+	ret = PTR_ERR_OR_ZERO(cpufreq_dt);
+	if (ret) {
+		dev_err(dev, "failed to create cpufreq-dt device: %d\n", ret);
+		goto detach_pm;
+	}
+
+	priv->cpufreq_dt = cpufreq_dt;
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+
+detach_pm:
+	dev_pm_domain_detach_list(priv->pd_list);
+clear_opp_config:
+	dev_pm_opp_clear_config(priv->opp_token);
+
+	return ret;
+}
+
+static void airoha_cpufreq_remove(struct platform_device *pdev)
+{
+	struct airoha_cpufreq_priv *priv = platform_get_drvdata(pdev);
+
+	platform_device_unregister(priv->cpufreq_dt);
+
+	dev_pm_domain_detach_list(priv->pd_list);
+
+	dev_pm_opp_clear_config(priv->opp_token);
+}
+
+static struct platform_driver airoha_cpufreq_driver = {
+	.probe = airoha_cpufreq_probe,
+	.remove = airoha_cpufreq_remove,
+	.driver = {
+		.name = "airoha-cpufreq",
+	},
+};
+
+static const struct of_device_id airoha_cpufreq_match_list[] __initconst = {
+	{ .compatible = "airoha,en7581" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, airoha_cpufreq_match_list);
+
+static int __init airoha_cpufreq_init(void)
+{
+	struct device_node *np = of_find_node_by_path("/");
+	const struct of_device_id *match;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	match = of_match_node(airoha_cpufreq_match_list, np);
+	of_node_put(np);
+	if (!match)
+		return -ENODEV;
+
+	ret = platform_driver_register(&airoha_cpufreq_driver);
+	if (unlikely(ret < 0))
+		return ret;
+
+	cpufreq_pdev = platform_device_register_data(NULL, "airoha-cpufreq",
+						     -1, match, sizeof(*match));
+	ret = PTR_ERR_OR_ZERO(cpufreq_pdev);
+	if (ret)
+		platform_driver_unregister(&airoha_cpufreq_driver);
+
+	return ret;
+}
+module_init(airoha_cpufreq_init);
+
+static void __exit airoha_cpufreq_exit(void)
+{
+	platform_device_unregister(cpufreq_pdev);
+	platform_driver_unregister(&airoha_cpufreq_driver);
+}
+module_exit(airoha_cpufreq_exit);
+
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_DESCRIPTION("CPUfreq driver for Airoha SoCs");
+MODULE_LICENSE("GPL");

drivers/cpufreq/cpufreq-dt-platdev.c

@@ -103,6 +103,8 @@ static const struct of_device_id allowlist[] __initconst = {
  * platforms using "operating-points-v2" property.
  */
 static const struct of_device_id blocklist[] __initconst = {
+	{ .compatible = "airoha,en7581", },
+
 	{ .compatible = "allwinner,sun50i-a100" },
 	{ .compatible = "allwinner,sun50i-h6", },
 	{ .compatible = "allwinner,sun50i-h616", },