nvmem: Add apple-spmi-nvmem driver

Add a driver for a series of SPMI-attached PMICs present on Apple devices

Reviewed-by: Neal Gompa <neal@gompa.dev>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Hector Martin <marcan@marcan.st>
Co-developed-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
Link: https://lore.kernel.org/r/20250509122452.11827-4-srini@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -2298,6 +2298,7 @@ F:	drivers/iommu/io-pgtable-dart.c
 F:	drivers/irqchip/irq-apple-aic.c
 F:	drivers/nvme/host/apple.c
 F:	drivers/nvmem/apple-efuses.c
+F:	drivers/nvmem/apple-spmi-nvmem.c
 F:	drivers/pinctrl/pinctrl-apple-gpio.c
 F:	drivers/pwm/pwm-apple.c
 F:	drivers/soc/apple/*

drivers/nvmem/Kconfig

@@ -40,6 +40,19 @@ config NVMEM_APPLE_EFUSES
 	  This driver can also be built as a module. If so, the module will
 	  be called nvmem-apple-efuses.
 
+config NVMEM_APPLE_SPMI
+	tristate "Apple SPMI NVMEM"
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on SPMI
+	select REGMAP_SPMI
+	help
+	  Say y here to build a driver to expose NVMEM cells for a set of power
+	  and RTC-related settings on a SPMI-attached PMIC present on Apple
+	  devices, such as Apple Silicon Macs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called apple-nvmem-spmi.
+
 config NVMEM_BCM_OCOTP
 	tristate "Broadcom On-Chip OTP Controller support"
 	depends on ARCH_BCM_IPROC || COMPILE_TEST

drivers/nvmem/Makefile

@@ -12,6 +12,8 @@ obj-y				+= layouts/
 # Devices
 obj-$(CONFIG_NVMEM_APPLE_EFUSES)	+= nvmem-apple-efuses.o
 nvmem-apple-efuses-y 			:= apple-efuses.o
+obj-$(CONFIG_NVMEM_APPLE_SPMI)		+= apple_nvmem_spmi.o
+apple_nvmem_spmi-y			:= apple-spmi-nvmem.o
 obj-$(CONFIG_NVMEM_BCM_OCOTP)		+= nvmem-bcm-ocotp.o
 nvmem-bcm-ocotp-y			:= bcm-ocotp.o
 obj-$(CONFIG_NVMEM_BRCM_NVRAM)		+= nvmem_brcm_nvram.o

drivers/nvmem/apple-spmi-nvmem.c

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SPMI 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/spmi.h>
+#include <linux/regmap.h>
+
+static const struct regmap_config apple_spmi_regmap_config = {
+	.reg_bits	= 16,
+	.val_bits	= 8,
+	.max_register	= 0xffff,
+};
+
+static int apple_spmi_nvmem_probe(struct spmi_device *sdev)
+{
+	struct regmap *regmap;
+	struct nvmem_config nvmem_cfg = {
+		.dev = &sdev->dev,
+		.name = "spmi_nvmem",
+		.id = NVMEM_DEVID_AUTO,
+		.word_size = 1,
+		.stride = 1,
+		.size = 0xffff,
+		.reg_read = (void *)regmap_bulk_read,
+		.reg_write = (void *)regmap_bulk_write,
+	};
+
+	regmap = devm_regmap_init_spmi_ext(sdev, &apple_spmi_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	nvmem_cfg.priv = regmap;
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(&sdev->dev, &nvmem_cfg));
+}
+
+static const struct of_device_id apple_spmi_nvmem_id_table[] = {
+	{ .compatible = "apple,spmi-nvmem" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, apple_spmi_nvmem_id_table);
+
+static struct spmi_driver apple_spmi_nvmem_driver = {
+	.probe = apple_spmi_nvmem_probe,
+	.driver = {
+		.name = "apple-spmi-nvmem",
+		.of_match_table	= apple_spmi_nvmem_id_table,
+	},
+};
+
+module_spmi_driver(apple_spmi_nvmem_driver);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_DESCRIPTION("Apple SPMI NVMEM driver");