[PATCH 6/6] nvmem: max77759: add Maxim MAX77759 NVMEM driver

André Draszik
2025-02-24T10:28:56Z

The Maxim MAX77759 is a companion Power Management IC for USB Type-C
applications with Battery Charger, Fuel Gauge, temperature sensors, USB
Type-C Port Controller (TCPC), NVMEM, and additional GPIO interfaces.

This driver exposes the non volatile memory using the platform device
registered by the core MFD driver.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
MAINTAINERS | 1 +
drivers/nvmem/Kconfig | 12 ++++
drivers/nvmem/Makefile | 2 +
drivers/nvmem/max77759-nvmem.c | 156 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 171 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index d119ed1ff279..bbc92dee7af4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14329,6 +14329,7 @@ S: Maintained
F: Documentation/devicetree/bindings/*/maxim,max77759*.yaml
F: drivers/gpio/gpio-max77759.c
F: drivers/mfd/max77759.c
+F: drivers/nvmem/max77759-nvmem.c
F: include/linux/mfd/max77759.h

MAXIM MAX77802 PMIC REGULATOR DEVICE DRIVER
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index 8671b7c974b9..3de07ef52490 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -154,6 +154,18 @@ config NVMEM_LPC18XX_OTP
To compile this driver as a module, choose M here: the module
will be called nvmem_lpc18xx_otp.

+config NVMEM_MAX77759
+ tristate "Maxim Integrated MAX77759 NVMEM Support"
+ depends on MFD_MAX77759
+ default MFD_MAX77759
+ help
+ Say Y here to include support for the user-accessible storage found
+ in Maxim Integrated MAX77759 PMICs. This IC provides space for 30
+ bytes of storage.
+
+ This driver can also be built as a module. If so, the module
+ will be called nvmem-max77759.
+
config NVMEM_MESON_EFUSE
tristate "Amlogic Meson GX eFuse Support"
depends on (ARCH_MESON || COMPILE_TEST) && MESON_SM
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 5b77bbb6488b..a9d03cfbbd27 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -34,6 +34,8 @@ obj-$(CONFIG_NVMEM_LPC18XX_EEPROM) += nvmem_lpc18xx_eeprom.o
nvmem_lpc18xx_eeprom-y := lpc18xx_eeprom.o
obj-$(CONFIG_NVMEM_LPC18XX_OTP) += nvmem_lpc18xx_otp.o
nvmem_lpc18xx_otp-y := lpc18xx_otp.o
+obj-$(CONFIG_NVMEM_MAX77759) += nvmem-max77759.o
+nvmem-max77759-y := max77759-nvmem.o
obj-$(CONFIG_NVMEM_MESON_EFUSE) += nvmem_meson_efuse.o
nvmem_meson_efuse-y := meson-efuse.o
obj-$(CONFIG_NVMEM_MESON_MX_EFUSE) += nvmem_meson_mx_efuse.o
diff --git a/drivers/nvmem/max77759-nvmem.c b/drivers/nvmem/max77759-nvmem.c
new file mode 100644
index 000000000000..4c455b242542
--- /dev/null
+++ b/drivers/nvmem/max77759-nvmem.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright 2020 Google Inc
+// Copyright 2025 Linaro Ltd.
+//
+// NVMEM driver for Maxim MAX77759
+
+#include <linux/dev_printk.h>
+#include <linux/device.h>
+#include <linux/device/driver.h>
+#include <linux/err.h>
+#include <linux/mfd/max77759.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/overflow.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+
+#define MAX77759_NVMEM_OPCODE_HEADER_LEN 3
+/*
+ * NVMEM commands have a three byte header (which becomes part of the command),
+ * so we need to subtract that.
+ */
+#define MAX77759_NVMEM_SIZE (MAX77759_MAXQ_OPCODE_MAXLENGTH \
+ - MAX77759_NVMEM_OPCODE_HEADER_LEN)
+
+struct max77759_nvmem {
+ struct device *dev;
+ struct max77759_mfd *max77759_mfd;
+};
+
+static bool max77759_nvmem_is_valid(unsigned int offset, size_t bytes)
+{
+ return (offset + bytes - 1 <= MAX77759_NVMEM_SIZE);
+}
+
+static int max77759_nvmem_reg_read(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct max77759_nvmem *nvmem = priv;
+ DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
+ MAX77759_NVMEM_OPCODE_HEADER_LEN);
+ DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
+ MAX77759_MAXQ_OPCODE_MAXLENGTH);
+ int ret;
+
+ if (!max77759_nvmem_is_valid(offset, bytes)) {
+ dev_err(nvmem->dev, "outside NVMEM area: %u / %zu\n",
+ offset, bytes);
+ return -EINVAL;
+ }
+
+ cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_READ;
+ cmd->cmd[1] = offset;
+ cmd->cmd[2] = bytes;
+ rsp->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
+
+ ret = max77759_maxq_command(nvmem->max77759_mfd, cmd, rsp);
+ if (ret < 0)
+ return ret;
+
+ if (memcmp(cmd->cmd, rsp->rsp, MAX77759_NVMEM_OPCODE_HEADER_LEN)) {
+ dev_warn(nvmem->dev, "protocol error (read)\n");
+ return -EIO;
+ }
+
+ memcpy(val, &rsp->rsp[MAX77759_NVMEM_OPCODE_HEADER_LEN], bytes);
+
+ return 0;
+}
+
+static int max77759_nvmem_reg_write(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct max77759_nvmem *nvmem = priv;
+ DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
+ MAX77759_MAXQ_OPCODE_MAXLENGTH);
+ DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
+ MAX77759_MAXQ_OPCODE_MAXLENGTH);
+ int ret;
+
+ if (!max77759_nvmem_is_valid(offset, bytes)) {
+ dev_err(nvmem->dev, "outside NVMEM area: %u / %zu\n",
+ offset, bytes);
+ return -EINVAL;
+ }
+
+ cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_WRITE;
+ cmd->cmd[1] = offset;
+ cmd->cmd[2] = bytes;
+ memcpy(&cmd->cmd[MAX77759_NVMEM_OPCODE_HEADER_LEN], val, bytes);
+ cmd->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
+ rsp->length = cmd->length;
+
+ ret = max77759_maxq_command(nvmem->max77759_mfd, cmd, rsp);
+ if (ret < 0)
+ return ret;
+
+ if (memcmp(cmd->cmd, rsp->rsp, cmd->length)) {
+ dev_warn(nvmem->dev, "protocol error (write)\n");
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int max77759_nvmem_probe(struct platform_device *pdev)
+{
+ struct nvmem_config config = {
+ .dev = &pdev->dev,
+ .name = dev_name(&pdev->dev),
+ .id = NVMEM_DEVID_NONE,
+ .type = NVMEM_TYPE_EEPROM,
+ .ignore_wp = true,
+ .size = MAX77759_NVMEM_SIZE,
+ .word_size = sizeof(u8),
+ .stride = sizeof(u8),
+ .reg_read = max77759_nvmem_reg_read,
+ .reg_write = max77759_nvmem_reg_write,
+ };
+ struct max77759_nvmem *nvmem;
+
+ nvmem = devm_kzalloc(&pdev->dev, sizeof(*nvmem), GFP_KERNEL);
+ if (!nvmem)
+ return -ENOMEM;
+
+ nvmem->dev = &pdev->dev;
+ nvmem->max77759_mfd = dev_get_drvdata(pdev->dev.parent);
+
+ config.priv = nvmem;
+
+ return PTR_ERR_OR_ZERO(devm_nvmem_register(config.dev, &config));
+}
+
+static const struct of_device_id max77759_nvmem_of_id[] = {
+ { .compatible = "maxim,max77759-nvmem", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, max77759_nvmem_of_id);
+
+static struct platform_driver max77759_nvmem_driver = {
+ .driver = {
+ .name = "max77759-nvmem",
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+ .of_match_table = max77759_nvmem_of_id,
+ },
+ .probe = max77759_nvmem_probe,
+};
+
+module_platform_driver(max77759_nvmem_driver);
+
+MODULE_AUTHOR("André Draszik <andre.draszik@linaro.org>");
+MODULE_DESCRIPTION("NVMEM driver for Maxim MAX77759");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:max77759-nvmem");

--
2.48.1.658.g4767266eb4-goog