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Message-ID: <CADrjBPqe6JsT_yKTazRn-Ro2V4ZHQ1=6LX304CyVxgzLBqXrew@mail.gmail.com>
Date: Fri, 12 Sep 2025 12:16:19 +0100
From: Peter Griffin <peter.griffin@...aro.org>
To: t.antoine@...ouvain.be
Cc: Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
Dimitri Fedrau <dima.fedrau@...il.com>, Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, André Draszik <andre.draszik@...aro.org>,
Tudor Ambarus <tudor.ambarus@...aro.org>, Alim Akhtar <alim.akhtar@...sung.com>,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v5 1/4] power: supply: add support for MAX77759 fuel gauge
Hi Thomas,
Thanks for your patch, and working on this!
On Mon, 4 Aug 2025 at 15:25, Thomas Antoine via B4 Relay
<devnull+t.antoine.uclouvain.be@...nel.org> wrote:
>
> From: Thomas Antoine <t.antoine@...ouvain.be>
>
> The Maxim MAX77759 is a PMIC used in gs101-oriole and gs101-raven
> (Google Pixel 6 and 6 Pro). It contains a fuel gauge on a separate
> I2C address. Add basic support for this fuel gauge. The driver is
> based on the driver for the MAX17201 and MAX17205 which also use
> the MAX M5 fuel gauge. There is a lot of common between the two
small nit: "in common" ^^^^^^
> devices with some key differences. The main one is the lack of nvmem
> in the fuel gauge of the MAX77759.
>
> The initialization of the chip is very basic and mostly hardcoded.
> Loading the model of the fuel gauge is not implemented here.
>
> On both gs101-oriole and gs101-raven, the same EEPROM as for the
> battery id is used to backup some of the state of the fuel gauge.
> Use a standard nvmem binding to access this data. The CRC8 is
> computed to allow to go from linux to a stock android without
> apparent data corruption. If other devices using the MAX77759 are
> found/created, a similar nvmem layout should be made or the driver
> should be extended to support those devices.
>
> The current, capacity, temperature and charge have all been tested.
> The charge full design and capacity equal the ones seen on android,
> the ratio between average charge and average current does predict
> pretty accurately the time to empty under a constant workload and
> temperature is coherent with the dynamic state of the device.
>
> Health is not enabled as it always reports overheating. The time to
> empty is wrong by about a factor 2. The voltage reporting is
> correct when using VCELL (which reports the lowest voltage of all
> cells) when considering that the device is connected to a single
> cell. It could be enabled by either confirming that the device is
> connected to a single cell or finding an alternative reporting mean.
>
> Modifications have been made to it since but the regmap was
> originally proposed by André Draszik in
>
> Link: https://lore.kernel.org/all/d1bade77b5281c1de6b2ddcb4dbbd033e455a116.camel@linaro.org/
>
> Signed-off-by: Thomas Antoine <t.antoine@...ouvain.be>
> ---
> drivers/power/supply/Kconfig | 14 +
> drivers/power/supply/Makefile | 1 +
> drivers/power/supply/max77759_battery.c | 649 ++++++++++++++++++++++++++++++++
> 3 files changed, 664 insertions(+)
>
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 79ddb006e2dad6bf96b71ed570a37c006b5f9433..147d049b836c3fbb24b762dbaf31eebb8ba041f7 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -458,6 +458,20 @@ config BATTERY_MAX1721X
> Say Y here to enable support for the MAX17211/MAX17215 standalone
> battery gas-gauge.
>
> +config BATTERY_MAX77759
> + tristate "Maxim Integrated MAX77759 Fuel Gauge"
> + depends on I2C
> + select REGMAP_I2C
> + help
> + Say yes to enable support for the Fuel gauge of the Maxim Integrated
> + MAX77759. It 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.
> +
> + To compile this driver as module, choose M here: the
> + module will be called max77759_fg.
> +
> config BATTERY_TWL4030_MADC
> tristate "TWL4030 MADC battery driver"
> depends on TWL4030_MADC
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index 4f5f8e3507f80da02812f0d08c2d81ddff0a272f..114578fa4fd08356822f13ce1fbad29923defad8 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -57,6 +57,7 @@ obj-$(CONFIG_BATTERY_MAX17040) += max17040_battery.o
> obj-$(CONFIG_BATTERY_MAX17042) += max17042_battery.o
> obj-$(CONFIG_BATTERY_MAX1720X) += max1720x_battery.o
> obj-$(CONFIG_BATTERY_MAX1721X) += max1721x_battery.o
> +obj-$(CONFIG_BATTERY_MAX77759) += max77759_battery.o
> obj-$(CONFIG_BATTERY_RT5033) += rt5033_battery.o
> obj-$(CONFIG_CHARGER_RT5033) += rt5033_charger.o
> obj-$(CONFIG_CHARGER_RT9455) += rt9455_charger.o
> diff --git a/drivers/power/supply/max77759_battery.c b/drivers/power/supply/max77759_battery.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..d8d702af607211e391733cd14323698b54be734c
> --- /dev/null
> +++ b/drivers/power/supply/max77759_battery.c
> @@ -0,0 +1,649 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Fuel gauge driver for Maxim 777759
> + *
> + * based on max1720x_battery.c
> + *
> + * Copyright (C) 2024 Liebherr-Electronics and Drives GmbH
> + */
> +
[..]
> + switch (psp) {
> + case POWER_SUPPLY_PROP_PRESENT:
> + /*
> + * POWER_SUPPLY_PROP_PRESENT will always readable via
> + * sysfs interface. Value return 0 if battery not
> + * present or unaccesable via I2c.
small nit: inaccessible ^^^^^^
> + */
> + ret = regmap_read(info->regmap, MAX77759_FG_STATUS, ®_val);
> + if (ret < 0) {
> + val->intval = 0;
> + return 0;
> + }
> +
> + val->intval = !FIELD_GET(MAX77759_FG_STATUS_BAT_ABSENT, reg_val);
> + break;
> + case POWER_SUPPLY_PROP_CAPACITY:
> + ret = regmap_read(info->regmap, MAX77759_FG_REPSOC, ®_val);
> + val->intval = max77759_fg_percent_to_ps(reg_val);
> + break;
> + case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
> + ret = regmap_read(info->regmap, MAX77759_FG_DESIGN_CAP, ®_val);
> + if (ret < 0)
> + return ret;
> +
> + val->intval = max77759_fg_capacity_to_ps(reg_val, info);
> + ret = max77759_fg_capacity_lsb(info, ®_val);
> + val->intval *= reg_val;
> + break;
> + case POWER_SUPPLY_PROP_CHARGE_AVG:
> + ret = regmap_read(info->regmap, MAX77759_FG_REPCAP, ®_val);
> + if (ret < 0)
> + return ret;
> +
> + val->intval = max77759_fg_capacity_to_ps(reg_val, info);
> + ret = max77759_fg_capacity_lsb(info, ®_val);
> + val->intval *= reg_val;
> + break;
> + case POWER_SUPPLY_PROP_TEMP:
> + ret = regmap_read(info->regmap, MAX77759_FG_TEMP, ®_val);
> + val->intval = max77759_fg_temperature_to_ps(reg_val);
> + break;
> + case POWER_SUPPLY_PROP_CURRENT_NOW:
> + ret = regmap_read(info->regmap, MAX77759_FG_CURRENT, ®_val);
> + val->intval = max77759_fg_current_to_voltage(reg_val) / info->rsense;
> + break;
> + case POWER_SUPPLY_PROP_CURRENT_AVG:
> + ret = regmap_read(info->regmap, MAX77759_FG_AVG_CURRENT, ®_val);
> + val->intval = max77759_fg_current_to_voltage(reg_val) / info->rsense;
> + break;
> + case POWER_SUPPLY_PROP_CHARGE_FULL:
> + ret = regmap_read(info->regmap, MAX77759_FG_FULL_CAP, ®_val);
> + if (ret < 0)
> + return ret;
> +
> + val->intval = max77759_fg_capacity_to_ps(reg_val, info);
> + ret = max77759_fg_capacity_lsb(info, ®_val);
> + val->intval *= reg_val;
> + break;
> + case POWER_SUPPLY_PROP_MODEL_NAME:
> + ret = regmap_read(info->regmap, MAX77759_FG_DEV_NAME, ®_val);
> + if (ret < 0)
> + return ret;
> +
> + reg_val = FIELD_GET(MAX77759_FG_DEV_NAME_TYPE_MASK, reg_val);
> + if (reg_val == MAX77759_FG_DEV_NAME_TYPE)
> + val->strval = max77759_fg_model;
> + else
> + return -ENODEV;
> + break;
> + case POWER_SUPPLY_PROP_MANUFACTURER:
> + val->strval = max77759_fg_manufacturer;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +static int max77759_fg_init(struct device *dev,
> + struct max77759_fg_device_info *info,
> + struct power_supply *bat_psy)
> +{
> + struct max77759_fg_state_save *state;
> + struct power_supply_battery_info *bat_info;
> + struct nvmem_cell *cell;
> + unsigned int val;
> + int ret;
> + size_t len;
> +
> + power_supply_get_battery_info(bat_psy, &bat_info);
Should check the return code here and exit if not present as if the
battery info is missing in DT it will crash in max77759_fg_init().
With that addressed:
Reviewed-by: Peter Griffin <peter.griffin@...aro.org>
I think there was also some feedback from Krysztof on the binding, but
aside from that I think Sebastian was ready to queue this.
regards,
Peter
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