[PATCH 1/2] cpufreq: Add sunxi nvmem based CPU scaling driver

[Yangtao Li]

For some SoCs, the CPU frequency subset and voltage value of each OPP
varies based on the silicon variant in use. Allwinner Process Voltage
Scaling Tables defines the voltage and frequency value  based on the
speedbin blown in the efuse combination. The sunxi-cpufreq-nvmem driver
reads the efuse value from the SoC to provide the OPP framework with
required information.

Signed-off-by: Yangtao Li <tiny.windzz@xxxxxxxxx>
---
 MAINTAINERS                           |   7 +
 drivers/cpufreq/Kconfig.arm           |  10 ++
 drivers/cpufreq/Makefile              |   1 +
 drivers/cpufreq/cpufreq-dt-platdev.c  |   2 +
 drivers/cpufreq/sunxi-cpufreq-nvmem.c | 236 ++++++++++++++++++++++++++
 5 files changed, 256 insertions(+)
 create mode 100644 drivers/cpufreq/sunxi-cpufreq-nvmem.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 391405091c6b..bfd18ba6aa1a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -667,6 +667,13 @@ S:	Maintained
 F:	Documentation/i2c/busses/i2c-ali1563
 F:	drivers/i2c/busses/i2c-ali1563.c
 
+ALLWINNER CPUFREQ DRIVER
+M:	Yangtao Li <tiny.windzz@xxxxxxxxx>
+L:	linux-pm@xxxxxxxxxxxxxxx
+S:	Maintained
+F:	Documentation/devicetree/bindings/opp/sunxi-nvmem-cpufreq.txt
+F:	drivers/cpufreq/sunxi-cpufreq-nvmem.c
+
 ALLWINNER SECURITY SYSTEM
 M:	Corentin Labbe <clabbe.montjoie@xxxxxxxxx>
 L:	linux-crypto@xxxxxxxxxxxxxxx
diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 179a1d302f48..25933c4321a7 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -18,6 +18,16 @@ config ACPI_CPPC_CPUFREQ
 
 	  If in doubt, say N.
 
+config ARM_ALLWINNER_CPUFREQ_NVMEM
+	tristate "Allwinner nvmem based CPUFreq"
+	depends on ARCH_SUNXI
+	depends on NVMEM_SUNXI_SID
+	select PM_OPP
+	help
+	  This adds the CPUFreq driver for Allwinner nvmem based SoC.
+
+	  If in doubt, say N.
+
 config ARM_ARMADA_37XX_CPUFREQ
 	tristate "Armada 37xx CPUFreq support"
 	depends on ARCH_MVEBU && CPUFREQ_DT
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 689b26c6f949..da28de67613c 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -78,6 +78,7 @@ obj-$(CONFIG_ARM_SCMI_CPUFREQ)		+= scmi-cpufreq.o
 obj-$(CONFIG_ARM_SCPI_CPUFREQ)		+= scpi-cpufreq.o
 obj-$(CONFIG_ARM_SPEAR_CPUFREQ)		+= spear-cpufreq.o
 obj-$(CONFIG_ARM_STI_CPUFREQ)		+= sti-cpufreq.o
+obj-$(CONFIG_ARM_ALLWINNER_CPUFREQ_NVMEM) += sunxi-cpufreq-nvmem.o
 obj-$(CONFIG_ARM_TANGO_CPUFREQ)		+= tango-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA20_CPUFREQ)	+= tegra20-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA124_CPUFREQ)	+= tegra124-cpufreq.o
diff --git a/drivers/cpufreq/cpufreq-dt-platdev.c b/drivers/cpufreq/cpufreq-dt-platdev.c
index 47729a22c159..50e7810f3a28 100644
--- a/drivers/cpufreq/cpufreq-dt-platdev.c
+++ b/drivers/cpufreq/cpufreq-dt-platdev.c
@@ -105,6 +105,8 @@ static const struct of_device_id whitelist[] __initconst = {
  * platforms using "operating-points-v2" property.
  */
 static const struct of_device_id blacklist[] __initconst = {
+	{ .compatible = "allwinner,sun50i-h6", },
+
 	{ .compatible = "calxeda,highbank", },
 	{ .compatible = "calxeda,ecx-2000", },
 
diff --git a/drivers/cpufreq/sunxi-cpufreq-nvmem.c b/drivers/cpufreq/sunxi-cpufreq-nvmem.c
new file mode 100644
index 000000000000..e189f94592d5
--- /dev/null
+++ b/drivers/cpufreq/sunxi-cpufreq-nvmem.c
@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Allwinner CPUFreq nvmem based driver
+ *
+ * Copyright (C) 2019 Yangtao Li <tiny.windzz@xxxxxxxxx>
+ */
+
+/*
+ * For some SoCs, the CPU frequency subset and voltage value of each OPP
+ * varies based on the silicon variant in use. Allwinner Process Voltage
+ * Scaling Tables defines the voltage and frequency value  based on the
+ * speedbin blown in the efuse combination. The sunxi-cpufreq-nvmem driver
+ * reads the efuse value from the SoC to provide the OPP framework with
+ * required information.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+
+struct sunxi_cpufreq_soc_data {
+	u32 (*efuse_xlate)(const struct sunxi_cpufreq_soc_data *soc_data,
+			   u32 efuse);
+	u32 nvmem_mask;
+	u32 nvmem_shift;
+};
+
+static struct platform_device *cpufreq_dt_pdev, *sunxi_cpufreq_pdev;
+
+static u32 sun50i_efuse_xlate(const struct sunxi_cpufreq_soc_data *soc_data,
+			  u32 efuse)
+{
+	return 1 << (efuse >> soc_data->nvmem_shift) & soc_data->nvmem_mask;
+}
+
+/**
+ * sunxi_cpufreq_get_efuse() - Parse and return efuse value present on SoC
+ * @soc_data: pointer to sunxi_cpufreq_soc_data context
+ * @versions: Set to the value parsed from efuse
+ *
+ * Returns 0 if success.
+ */
+static int sunxi_cpufreq_get_efuse(const struct sunxi_cpufreq_soc_data *soc_data,
+				   u32 *versions)
+{
+	struct nvmem_cell *speedbin_nvmem;
+	struct device_node *np;
+	struct device *cpu_dev;
+	u32 *speedbin;
+	size_t len;
+	int ret;
+
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev)
+		return -ENODEV;
+
+	np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
+	if (!np)
+		return -ENOENT;
+
+	ret = of_device_is_compatible(np, "operating-points-v2-sunxi-cpu");
+	if (!ret) {
+		of_node_put(np);
+		return -ENOENT;
+	}
+
+	speedbin_nvmem = of_nvmem_cell_get(np, NULL);
+	of_node_put(np);
+	if (IS_ERR(speedbin_nvmem)) {
+		if (PTR_ERR(speedbin_nvmem) != -EPROBE_DEFER)
+			pr_err("Could not get nvmem cell: %ld\n",
+				PTR_ERR(speedbin_nvmem));
+		return PTR_ERR(speedbin_nvmem);
+	}
+
+	speedbin = nvmem_cell_read(speedbin_nvmem, &len);
+	nvmem_cell_put(speedbin_nvmem);
+	if (IS_ERR(speedbin))
+		return PTR_ERR(speedbin);
+
+	*versions = soc_data->efuse_xlate(soc_data, *speedbin);
+
+	kfree(speedbin);
+	return 0;
+};
+
+static const struct sunxi_cpufreq_soc_data sun50i_h6_data = {
+	.efuse_xlate = sun50i_efuse_xlate,
+	.nvmem_mask = 0x7,
+	.nvmem_shift = 5,
+};
+
+static const struct of_device_id sunxi_cpufreq_match_list[] = {
+	{ .compatible = "allwinner,sun50i-h6", .data = &sun50i_h6_data },
+	{}
+};
+
+static const struct of_device_id *sunxi_cpufreq_match_node(void)
+{
+	struct device_node *np;
+	const struct of_device_id *match;
+
+	np = of_find_node_by_path("/");
+	match = of_match_node(sunxi_cpufreq_match_list, np);
+	of_node_put(np);
+
+	return match;
+}
+
+static int sunxi_cpufreq_nvmem_probe(struct platform_device *pdev)
+{
+	const struct sunxi_cpufreq_soc_data *soc_data;
+	struct opp_table **opp_tables;
+	const struct of_device_id *match;
+	unsigned int cpu;
+	u32 versions;
+	int ret;
+
+	opp_tables = kcalloc(num_possible_cpus(), sizeof(*opp_tables),
+			     GFP_KERNEL);
+	if (!opp_tables)
+		return -ENOMEM;
+
+	match = sunxi_cpufreq_match_node();
+	soc_data = match->data;
+	if (!soc_data)
+		return -EINVAL;
+
+	ret = sunxi_cpufreq_get_efuse(soc_data, &versions);
+	if (ret)
+		return ret;
+
+	for_each_possible_cpu(cpu) {
+		struct device *cpu_dev = get_cpu_device(cpu);
+
+		if (NULL == cpu_dev) {
+			ret = -ENODEV;
+			goto free_opp;
+		}
+
+		opp_tables[cpu] = dev_pm_opp_set_supported_hw(cpu_dev,
+							      &versions, 1);
+		if (IS_ERR(opp_tables[cpu])) {
+			ret = PTR_ERR(opp_tables[cpu]);
+			pr_err("Failed to set supported hardware\n");
+			goto free_opp;
+		}
+	}
+
+	cpufreq_dt_pdev = platform_device_register_simple("cpufreq-dt", -1,
+							  NULL, 0);
+	if (!IS_ERR(cpufreq_dt_pdev)) {
+		platform_set_drvdata(pdev, opp_tables);
+		return 0;
+	}
+
+	ret = PTR_ERR(cpufreq_dt_pdev);
+	pr_err("Failed to register platform device\n");
+
+free_opp:
+	for_each_possible_cpu(cpu) {
+		if (IS_ERR_OR_NULL(opp_tables[cpu]))
+			break;
+		dev_pm_opp_put_supported_hw(opp_tables[cpu]);
+	}
+	kfree(opp_tables);
+
+	return ret;
+}
+
+static int sunxi_cpufreq_nvmem_remove(struct platform_device *pdev)
+{
+	struct opp_table **opp_tables = platform_get_drvdata(pdev);
+	unsigned int cpu;
+
+	platform_device_unregister(cpufreq_dt_pdev);
+
+	for_each_possible_cpu(cpu)
+		dev_pm_opp_put_supported_hw(opp_tables[cpu]);
+
+	kfree(opp_tables);
+
+	return 0;
+}
+
+static struct platform_driver sunxi_cpufreq_driver = {
+	.probe = sunxi_cpufreq_nvmem_probe,
+	.remove = sunxi_cpufreq_nvmem_remove,
+	.driver = {
+		.name = "sunxi-cpufreq-nvmem",
+	},
+};
+
+/*
+ * Since the driver depends on nvmem drivers, which may return EPROBE_DEFER,
+ * all the real activity is done in the probe, which may be defered as well.
+ * The init here is only registering the driver and the platform device.
+ */
+static int __init sunxi_cpufreq_init(void)
+{
+	const struct of_device_id *match;
+	int ret;
+
+	match = sunxi_cpufreq_match_node();
+	if (!match)
+		return -ENODEV;
+
+	ret = platform_driver_register(&sunxi_cpufreq_driver);
+	if (unlikely(ret < 0))
+		return ret;
+
+	sunxi_cpufreq_pdev = platform_device_register_simple(
+		"sunxi-cpufreq-nvmem", -1, NULL, 0);
+	ret = PTR_ERR_OR_ZERO(sunxi_cpufreq_pdev);
+	if (0 == ret)
+		return 0;
+
+	platform_driver_unregister(&sunxi_cpufreq_driver);
+	return ret;
+}
+module_init(sunxi_cpufreq_init);
+
+static void __exit sunxi_cpufreq_exit(void)
+{
+	platform_device_unregister(sunxi_cpufreq_pdev);
+	platform_driver_unregister(&sunxi_cpufreq_driver);
+}
+module_exit(sunxi_cpufreq_exit);
+
+MODULE_DESCRIPTION("Sunxi cpufreq driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.0