Re: [PATCH v9 6/6] nvmem: max77759: add Maxim MAX77759 NVMEM driver

[Srinivas Kandagatla <srini@kernel.org>]

On Wed, Apr 30, 2025 at 10:03:13AM +0100, André Draszik wrote:
> The Maxim MAX77759 is a companion PMIC for USB Type-C applications and
> includes Battery Charger, Fuel Gauge, temperature sensors, USB Type-C
> Port Controller (TCPC), NVMEM, and a GPIO expander.
> 
> 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>

If the plan is to take this series via mfd here is my Ack

Acked-by: Srinivas Kandagatla <srini@kernel.org>

thanks,
Srini
> ---
> v9:
> * drop superfluous max77759_nvmem_is_valid() (Srini)
> 
> v8:
> * replace MODULE_ALIAS() with .id_table (Krzysztof)
> * drop previous tags
> 
> v5:
> * follow API updates of max77759 core driver
> 
> v2:
> * align sentinel in max77759_nvmem_of_id[] with other max77759 drivers
>  (Christophe)
> ---
>  MAINTAINERS                    |   1 +
>  drivers/nvmem/Kconfig          |  12 ++++
>  drivers/nvmem/Makefile         |   2 +
>  drivers/nvmem/max77759-nvmem.c | 145 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 160 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0db5e1fe64930e85265913e6a7dd2669c645cf42..b821502afc48f95d48fb8c6ac6941d1dd8e63582 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14670,6 +14670,7 @@ 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 8671b7c974b933e147154bb40b5d41b5730518d2..3de07ef524906ad24a89e58abdfe93529a83c80f 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 5b77bbb6488bf89bfb305750a1cbf4a6731a0a58..a9d03cfbbd27e68d40f8c330e72e20378b12a481 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 0000000000000000000000000000000000000000..c9961ad0e232e152e924b5b06d7d93172760ac3a
> --- /dev/null
> +++ b/drivers/nvmem/max77759-nvmem.c
> @@ -0,0 +1,145 @@
> +// 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 *max77759;
> +};
> +
> +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;
> +
> +	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, 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;
> +
> +	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, 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 = 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 const struct platform_device_id max77759_nvmem_platform_id[] = {
> +	{ "max77759-nvmem", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(platform, max77759_nvmem_platform_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,
> +	.id_table = max77759_nvmem_platform_id,
> +};
> +
> +module_platform_driver(max77759_nvmem_driver);
> +
> +MODULE_AUTHOR("André Draszik <andre.draszik@linaro.org>");
> +MODULE_DESCRIPTION("NVMEM driver for Maxim MAX77759");
> +MODULE_LICENSE("GPL");
> 
> -- 
> 2.49.0.901.g37484f566f-goog
>