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

Srinivas Kandagatla
2025-03-12T09:29:59Z

On 24/02/2025 10:28, André Draszik wrote:
> 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>
> ---
LGTM,

Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@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");
>