nvmem: Add spmi-mfd-nvmem driver

This driver exposes part of an SPMI MFD device as an NVMEM device.
It is intended to be used with e.g. PMUs/PMICs that are used to
hold power-management configuration, such as used on Apple Silicon
Macs.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

drivers/nvmem/Kconfig

@@ -299,6 +299,19 @@ config NVMEM_SNVS_LPGPR
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem-snvs-lpgpr.
 
+config NVMEM_SPMI_MFD
+	tristate "Generic SPMI MFD NVMEM"
+	depends on MFD_SIMPLE_MFD_SPMI || COMPILE_TEST
+	default ARCH_APPLE
+	help
+	  Say y here to build a generic driver to expose an SPMI MFD device
+	  as a NVMEM provider. This can be used for PMIC/PMU devices which
+	  are used to store power and RTC-related settings on certain
+	  platforms, such as Apple Silicon Macs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nvmem-spmi-mfd.
+
 config NVMEM_SPMI_SDAM
 	tristate "SPMI SDAM Support"
 	depends on SPMI

drivers/nvmem/Makefile

@@ -62,6 +62,8 @@ obj-$(CONFIG_NVMEM_SC27XX_EFUSE)	+= nvmem-sc27xx-efuse.o
 nvmem-sc27xx-efuse-y			:= sc27xx-efuse.o
 obj-$(CONFIG_NVMEM_SNVS_LPGPR)		+= nvmem_snvs_lpgpr.o
 nvmem_snvs_lpgpr-y			:= snvs_lpgpr.o
+obj-$(CONFIG_NVMEM_SPMI_MFD)		+= nvmem_spmi_mfd.o
+nvmem_spmi_mfd-y 			:= spmi-mfd-nvmem.o
 obj-$(CONFIG_NVMEM_SPMI_SDAM)		+= nvmem_qcom-spmi-sdam.o
 nvmem_qcom-spmi-sdam-y			+= qcom-spmi-sdam.o
 obj-$(CONFIG_NVMEM_SPRD_EFUSE)		+= nvmem_sprd_efuse.o

drivers/nvmem/spmi-mfd-nvmem.c

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Generic SPMI MFD NVMEM driver
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+struct spmi_mfd_nvmem {
+	struct regmap *regmap;
+	unsigned int base;
+};
+
+static int spmi_mfd_nvmem_read(void *priv, unsigned int offset,
+                               void *val, size_t bytes)
+{
+	struct spmi_mfd_nvmem *nvmem = priv;
+
+        return regmap_bulk_read(nvmem->regmap, nvmem->base + offset, val, bytes);
+}
+
+static int spmi_mfd_nvmem_write(void *priv, unsigned int offset,
+                                void *val, size_t bytes)
+{
+	struct spmi_mfd_nvmem *nvmem = priv;
+
+	return regmap_bulk_write(nvmem->regmap, nvmem->base + offset, val, bytes);
+}
+
+static int spmi_mfd_nvmem_probe(struct platform_device *pdev)
+{
+	struct spmi_mfd_nvmem *nvmem;
+	const __be32 *addr;
+	int len;
+	struct nvmem_config nvmem_cfg = {
+		.dev = &pdev->dev,
+		.name = "spmi_mfd_nvmem",
+		.id = NVMEM_DEVID_AUTO,
+		.word_size = 1,
+		.stride = 1,
+		.reg_read = spmi_mfd_nvmem_read,
+		.reg_write = spmi_mfd_nvmem_write,
+	};
+
+	nvmem = devm_kzalloc(&pdev->dev, sizeof(*nvmem), GFP_KERNEL);
+	if (!nvmem)
+		return -ENOMEM;
+
+	nvmem_cfg.priv = nvmem;
+
+	nvmem->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!nvmem->regmap) {
+		dev_err(&pdev->dev, "Parent regmap unavailable.\n");
+		return -ENXIO;
+	}
+
+	addr = of_get_property(pdev->dev.of_node, "reg", &len);
+	if (!addr) {
+		dev_err(&pdev->dev, "no reg property\n");
+		return -EINVAL;
+	}
+	if (len != 2 * sizeof(u32)) {
+		dev_err(&pdev->dev, "invalid reg property\n");
+		return -EINVAL;
+	}
+
+	nvmem->base = be32_to_cpup(&addr[0]);
+	nvmem_cfg.size = be32_to_cpup(&addr[1]);
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(&pdev->dev, &nvmem_cfg));
+}
+
+static const struct of_device_id spmi_mfd_nvmem_id_table[] = {
+	{ .compatible = "apple,spmi-pmu-nvmem" },
+	{ .compatible = "spmi-mfd-nvmem" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, spmi_mfd_nvmem_id_table);
+
+static struct platform_driver spmi_mfd_nvmem_driver = {
+	.probe = spmi_mfd_nvmem_probe,
+	.driver = {
+		.name = "spmi-mfd-nvmem",
+		.of_match_table	= spmi_mfd_nvmem_id_table,
+	},
+};
+
+module_platform_driver(spmi_mfd_nvmem_driver);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_DESCRIPTION("SPMI MFD NVMEM driver");