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>
---
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 | 162 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 177 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..df7d1998fa2f116450d2fd50eba70d9b61a24574
--- /dev/null
+++ b/drivers/nvmem/max77759-nvmem.c
@@ -0,0 +1,162 @@
+// 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 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, 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, 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

On Tue, Apr 29, 2025 at 09:21:42AM +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>
> ---
> 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 | 162 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 177 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..df7d1998fa2f116450d2fd50eba70d9b61a24574
> --- /dev/null
> +++ b/drivers/nvmem/max77759-nvmem.c
> @@ -0,0 +1,162 @@
> +// 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 bool max77759_nvmem_is_valid(unsigned int offset, size_t bytes)
> +{
> +	return (offset + bytes - 1 <= MAX77759_NVMEM_SIZE);
> +}
Do you really need this check?
nvmem core should take care of this boundary checks.

> +
> +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;
> +	}
> +

On Tue, 2025-04-29 at 20:51 +0100, Srinivas Kandagatla wrote:
> On Tue, Apr 29, 2025 at 09:21:42AM +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>
> > ---
> > 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 | 162 +++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 177 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..df7d1998fa2f116450d2fd50eba70d9b61a24574
> > --- /dev/null
> > +++ b/drivers/nvmem/max77759-nvmem.c
> > @@ -0,0 +1,162 @@
> > +// 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 bool max77759_nvmem_is_valid(unsigned int offset, size_t bytes)
> > +{
> > +	return (offset + bytes - 1 <= MAX77759_NVMEM_SIZE);
> > +}
> Do you really need this check?
> nvmem core should take care of this boundary checks.

I think I went by what qcom-spmi-sdam is doing, but I now realise it's
doing a little bit more. Will drop.

Thanks Srini!

A.