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([2a00:79e0:2e7c:8:7fdc:abb8:fa2e:d750]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b73a692222sm1153673eec.6.2026.01.22.16.07.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Jan 2026 16:07:49 -0800 (PST) Message-ID: Date: Thu, 22 Jan 2026 16:07:47 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/5] power: supply: max77759: add charger driver To: =?UTF-8?Q?Andr=C3=A9_Draszik?= , Sebastian Reichel , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Lee Jones , Greg Kroah-Hartman , Badhri Jagan Sridharan , Heikki Krogerus , Peter Griffin , Tudor Ambarus , Alim Akhtar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, RD Babiera , Kyle Tso References: <20260121-max77759-charger-v4-0-694234c8ded1@google.com> <20260121-max77759-charger-v4-4-694234c8ded1@google.com> <71d816c5ed4ee2d13ec63b8fd4acd49f4e418284.camel@linaro.org> Content-Language: en-US From: Amit Sunil Dhamne In-Reply-To: <71d816c5ed4ee2d13ec63b8fd4acd49f4e418284.camel@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Andre', On 1/22/26 4:47 AM, André Draszik wrote: > Hi Amit, > > Thanks for your patches, just a few minor comments below. Thanks for your feedback! > > On Wed, 2026-01-21 at 00:59 +0000, Amit Sunil Dhamne via B4 Relay wrote: >> From: Amit Sunil Dhamne >> >> Add support for MAX77759 battery charger driver. This is a 4A 1-Cell >> Li+/LiPoly dual input switch mode charger. While the device can support >> USB & wireless charger inputs, this implementation only supports USB >> input. This implementation supports both buck and boost modes. >> >> Signed-off-by: Amit Sunil Dhamne >> --- >>  MAINTAINERS                             |   6 + >>  drivers/power/supply/Kconfig            |  11 + >>  drivers/power/supply/Makefile           |   1 + >>  drivers/power/supply/max77759_charger.c | 737 ++++++++++++++++++++++++++++++++ >>  4 files changed, 755 insertions(+) >> >> diff --git a/MAINTAINERS b/MAINTAINERS >> index 0d044a58cbfe0f2b97f3682a86708e1ece108e9f..38354964a85c34611b1b54e20651b360f3b9c11e 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -15546,6 +15546,12 @@ F: drivers/mfd/max77759.c >>  F: drivers/nvmem/max77759-nvmem.c >>  F: include/linux/mfd/max77759.h >> >> +MAXIM MAX77759 BATTERY CHARGER DRIVER >> +M: Amit Sunil Dhamne >> +L: linux-kernel@vger.kernel.org >> +S: Maintained >> +F: drivers/power/supply/max77759_charger.c >> + >>  MAXIM MAX77802 PMIC REGULATOR DEVICE DRIVER >>  M: Javier Martinez Canillas >>  L: linux-kernel@vger.kernel.org >> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig >> index 92f9f7aae92f249aa165e68dbcd4cebb569286ea..3a2cdb95c98e44324151ac2b86d740ae2923ee77 100644 >> --- a/drivers/power/supply/Kconfig >> +++ b/drivers/power/supply/Kconfig >> @@ -631,6 +631,17 @@ config CHARGER_MAX77705 >>   help >>     Say Y to enable support for the Maxim MAX77705 battery charger. >> >> +config CHARGER_MAX77759 >> + tristate "Maxim MAX77759 battery charger driver" >> + depends on MFD_MAX77759 && REGULATOR >> + default MFD_MAX77759 >> + help >> +   Say M or Y here to enable the MAX77759 battery charger. MAX77759 >> +   charger is a function of the MAX77759 PMIC. This is a dual input >> +   switch-mode charger. This driver supports buck and OTG boost modes. >> + >> +   If built as a module, it will be called max77759_charger. >> + >>  config CHARGER_MAX77976 >>   tristate "Maxim MAX77976 battery charger driver" >>   depends on I2C >> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile >> index 4b79d5abc49a7fd1e37a26d0c89f94d9fe3a916f..6af905875ad5e3b393a7030405355b9a975870f6 100644 >> --- a/drivers/power/supply/Makefile >> +++ b/drivers/power/supply/Makefile >> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE) += surface_charger.o >>  obj-$(CONFIG_BATTERY_UG3105) += ug3105_battery.o >>  obj-$(CONFIG_CHARGER_QCOM_SMB2) += qcom_smbx.o >>  obj-$(CONFIG_FUEL_GAUGE_MM8013) += mm8013.o >> +obj-$(CONFIG_CHARGER_MAX77759) += max77759_charger.o >> diff --git a/drivers/power/supply/max77759_charger.c b/drivers/power/supply/max77759_charger.c >> new file mode 100644 >> index 0000000000000000000000000000000000000000..34b5ea0967eb7b4716e81ee1a55227ac872493b0 >> --- /dev/null >> +++ b/drivers/power/supply/max77759_charger.c >> @@ -0,0 +1,737 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * max77759_charger.c - Battery charger driver for MAX77759 charger device. >> + * >> + * Copyright 2025 Google LLC. >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +/* Default values for Fast Charge Current & Float Voltage */ >> +#define CHG_CC_DEFAULT_UA 2266770 >> +#define CHG_FV_DEFAULT_MV 4300 >> + >> +#define FOREACH_IRQ(S) \ >> + S(AICL), \ >> + S(CHGIN), \ >> + S(CHG), \ >> + S(INLIM), \ >> + S(BAT_OILO), \ >> + S(CHG_STA_CC), \ >> + S(CHG_STA_CV), \ >> + S(CHG_STA_TO), \ >> + S(CHG_STA_DONE) >> + >> +#define GENERATE_ENUM(e) e >> +#define GENERATE_STRING(s) #s >> + >> +enum { >> + FOREACH_IRQ(GENERATE_ENUM) >> +}; >> + >> +static const char *const chgr_irqs_str[] = { >> + FOREACH_IRQ(GENERATE_STRING) >> +}; >> + >> +#define NUM_IRQS ARRAY_SIZE(chgr_irqs_str) >> + >> +struct max77759_charger { >> + struct device *dev; >> + struct regmap *regmap; >> + struct power_supply *psy; >> + struct regulator_dev *chgin_otg_rdev; >> + struct notifier_block nb; >> + struct power_supply *tcpm_psy; >> + struct work_struct psy_work; >> + int irqs[NUM_IRQS]; >> + struct mutex lock; /* protects the state below */ >> + enum max77759_chgr_mode mode; >> +}; >> + >> +static inline int regval_to_val(int reg, int reg_offset, int step, int minval) >> +{ >> + return ((reg - reg_offset) * step) + minval; >> +} >> + >> +static inline int val_to_regval(int val, int minval, int step, int reg_offset) >> +{ >> + s64 dividend; >> + >> + if (unlikely(step == 0)) >> + return reg_offset; > Does it really make an impact on performance to specify unlikely? Also, I seem to > remember that the if branch is treated as unlikely anyway, but can't find any hard > evidence on that right now. I was hoping it's performance improving even if negligible, though I don't have evidence to support either arguments. In any case, I kept it for readability. > >> + >> + dividend = (s64)val - minval; >> + return DIV_S64_ROUND_CLOSEST(dividend, step) + reg_offset; >> +} > For these two functions above, have you considered using the APIs from > include/linux/linear_range.h instead of duplicating in this driver? The > implementations of the above match linear_range_get_value() and > linear_range_get_selector_low() quite nicely. I think it looks useful, will check it out. >> + >> +static inline int unlock_prot_regs(struct max77759_charger *chg, bool unlock) >> +{ >> + return regmap_update_bits(chg->regmap, MAX77759_CHGR_REG_CHG_CNFG_06, >> +   MAX77759_CHGR_REG_CHG_CNFG_06_CHGPROT, unlock >> +   ? MAX77759_CHGR_REG_CHG_CNFG_06_CHGPROT : 0); >> +} >> + > [...] > >> +static irqreturn_t irq_handler(int irq, void *data) >> +{ >> + struct max77759_charger *chg = data; >> + struct device *dev = chg->dev; >> + int i; >> + >> + for (i = 0; i < NUM_IRQS && chg->irqs[i] != irq; i++) >> + ; >> + >> + if (i == NUM_IRQS) { >> + dev_err(dev, "Unable to handle irq=%d", irq); >> + return IRQ_NONE; >> + } else if (i == BAT_OILO) { >> + dev_warn(dev, "Battery over-current threshold crossed"); >> + } > Generally, no 'else' is required after return. I will refactor it in the next rev. >> + >> + power_supply_changed(chg->psy); >> + return IRQ_HANDLED; >> +} >> + > [...] > >> +static void psy_work_item(struct work_struct *work) >> +{ >> + struct max77759_charger *chg = >> + container_of(work, struct max77759_charger, psy_work); >> + union power_supply_propval current_limit, online; >> + int ret; >> + >> + ret = power_supply_get_property(chg->tcpm_psy, >> + POWER_SUPPLY_PROP_CURRENT_MAX, >> + ¤t_limit); >> + if (ret) { >> + dev_err(chg->dev, >> + "Failed to get CURRENT_MAX psy property, ret=%d", >> + ret); >> + return; >> + } >> + >> + ret = power_supply_get_property(chg->tcpm_psy, POWER_SUPPLY_PROP_ONLINE, >> + &online); >> + if (ret) { >> + dev_err(chg->dev, >> + "Failed to get ONLINE psy property, ret=%d", >> + ret); >> + return; >> + } >> + >> + if (online.intval && current_limit.intval) { >> + ret = set_input_current_limit(chg, current_limit.intval); >> + if (ret) >> + dev_err(chg->dev, >> + "Unable to set current limit, ret=%d", ret); >> + >> + charger_set_mode(chg, MAX77759_CHGR_MODE_CHG_BUCK_ON); >> + } else { >> + charger_set_mode(chg, MAX77759_CHGR_MODE_OFF); >> + } > For all the possible errors in this function, should the driver try a bit > harder, even if unlikely to occur? Maybe we can do this: On failure of either of the power_supply_get_property() calls or set_input_current_limit(), we should first turn off the charger (as that's the safest choice) and reschedule this work for a certain number of times (maybe 3). Obviously, if we recover from this state, we reset the error limit and don't reschedule this work anymore. Do you concur? > What if the current limit needed to be > reduced, e.g. due to thermal or any other reasons? This specific piece of code is for setting current limit that is driven by USB Type-C subsystem. If the Type-C subsystem re-negotiates a PD contract this piece of code will re-run as this subsystem will be re-notified by TCPM. For cases where we need to cap the current limit due to thermal management, that's a hardware driven feature. It is enabled by enabling JEITA management. That's not in the scope atm. > > Could rescheduling the work be something to consider? > Responded in the previous comment.. >> +} >> + >> +static int psy_changed(struct notifier_block *nb, unsigned long evt, void *data) >> +{ >> + struct max77759_charger *chg = container_of(nb, struct max77759_charger, >> +     nb); >> + const char *psy_name = "tcpm-source"; > This can be static const char. Will fix it. > >> + struct power_supply *psy = data; >> + >> + if (!strnstr(psy->desc->name, psy_name, strlen(psy_name)) || >> +     evt != PSY_EVENT_PROP_CHANGED) >> + return NOTIFY_OK; >> + >> + chg->tcpm_psy = psy; >> + schedule_work(&chg->psy_work); >> + >> + return NOTIFY_OK; >> +} >> + >> +static void max_tcpci_unregister_psy_notifier(void *nb) >> +{ >> + power_supply_unreg_notifier(nb); >> +} >> + >> +static int max77759_charger_probe(struct platform_device *pdev) >> +{ >> + struct regulator_config chgin_otg_reg_cfg; >> + struct power_supply_config psy_cfg; >> + struct device *dev = &pdev->dev; >> + struct max77759_charger *chg; >> + int ret; >> + >> + device_set_of_node_from_dev(dev, dev->parent); >> + chg = devm_kzalloc(dev, sizeof(*chg), GFP_KERNEL); >> + if (!chg) >> + return -ENOMEM; >> + >> + platform_set_drvdata(pdev, chg); >> + chg->dev = dev; >> + chg->regmap = dev_get_regmap(dev->parent, "charger"); >> + if (!chg->regmap) >> + return dev_err_probe(dev, -ENODEV, "Missing regmap"); >> + >> + ret = devm_mutex_init(dev, &chg->lock); >> + if (ret) >> + return dev_err_probe(dev, ret, "Failed to initialize lock"); >> + >> + psy_cfg.fwnode = dev_fwnode(dev); >> + psy_cfg.drv_data = chg; >> + chg->psy = devm_power_supply_register(dev, &max77759_charger_desc, >> +       &psy_cfg); >> + if (IS_ERR(chg->psy)) >> + return dev_err_probe(dev, -EPROBE_DEFER, >> +      "Failed to register psy, ret=%ld", >> +      PTR_ERR(chg->psy)); >> + >> + ret = max77759_charger_init(chg); >> + if (ret) >> + return dev_err_probe(dev, ret, >> +      "Failed to initialize max77759 charger"); >> + >> + chgin_otg_reg_cfg.dev = dev; >> + chgin_otg_reg_cfg.driver_data = chg; >> + chgin_otg_reg_cfg.of_node = dev_of_node(dev); >> + chg->chgin_otg_rdev = devm_regulator_register(dev, &chgin_otg_reg_desc, >> +       &chgin_otg_reg_cfg); >> + if (IS_ERR(chg->chgin_otg_rdev)) >> + return dev_err_probe(dev, PTR_ERR(chg->chgin_otg_rdev), >> +      "Failed to register chgin otg regulator"); >> + >> + ret = devm_work_autocancel(dev, &chg->psy_work, psy_work_item); >> + if (ret) >> + return dev_err_probe(dev, ret, "Failed to initialize psy work"); >> + >> + chg->nb.notifier_call = psy_changed; >> + ret = power_supply_reg_notifier(&chg->nb); >> + if (ret) >> + return dev_err_probe(dev, ret, >> +      "Unable to register psy notifier"); >> + >> + ret = devm_add_action_or_reset(dev, max_tcpci_unregister_psy_notifier, >> +        &chg->nb); >> + if (ret) >> + return dev_err_probe(dev, ret, >> +      "Failed to add devm action to unregister psy notifier"); >> + >> + return max77759_init_irqhandler(chg); >> +} >> + >> +static const struct platform_device_id max77759_charger_id[] = { >> + {"max77759-charger",}, > Minor formatting nit - I believe common practice is to use named initializers: > > + { .compatible = "max77759-charger", }, Will fix. > >> + { } >> +}; >> +MODULE_DEVICE_TABLE(platform, max77759_charger_id); >> + >> +static struct platform_driver max77759_charger_driver = { >> + .driver = { >> + .name = "max77759-charger", > Can it be async, or are there issues with that? > > .probe_type = PROBE_PREFER_ASYNCHRONOUS, I don't think adding this should be an issue as this driver has very few dependencies. I will test it and add this in my next revision. > > Thanks again Amit! You're welcome! BR, Amit > > Cheers, > Andre' > >> + }, >> + .probe = max77759_charger_probe, >> + .id_table = max77759_charger_id, >> +}; >> +module_platform_driver(max77759_charger_driver); >> + >> +MODULE_AUTHOR("Amit Sunil Dhamne "); >> +MODULE_DESCRIPTION("Maxim MAX77759 charger driver"); >> +MODULE_LICENSE("GPL");