Date:   Sat, 16 Jan 2021 14:23:07 +0100
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Daisuke Nojiri <dnojiri@...omium.org>
Cc:     Guenter Roeck <linux@...ck-us.net>, vpalatin@...omium.org,
        Lee Jones <lee.jones@...aro.org>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Sebastian Reichel <sre@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Mark Brown <broonie@...nel.org>,
        Pi-Hsun Shih <pihsun@...omium.org>,
        Alex Levin <levinale@...gle.com>,
        Gwendal Grignou <gwendal@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Vijay Hiremath <vijay.p.hiremath@...el.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/2] power: supply: PCHG: Peripheral device charger

Hi,

This is mostly meant to forward Guenter's, so that it's recorded
by lore.kernel.org and Daisuke. I only had a quick look myself so
far assuming a new version would appear soon without noticing
Guenter's mail having interesting headers resulting in most people
probably not having received it.

IIUIC this is always reports the battery/charging status of
peripherals and not from the system itself? In that case please also
provide POWER_SUPPLY_PROP_SCOPE and return POWER_SUPPLY_SCOPE_DEVICE.

Also type=Wireless is meant to be used for wireless/inductive
chargers (e.g. Qi wireless charging). Peripherals set type=Battery,
see e.g. drivers/hid/hid-steam.c or drivers/hid/hid-sony.c.

-- Sebastian

On Wed, Dec 16, 2020 at 10:23:30AM -0800, Guenter Roeck wrote:
> On Wed, Dec 16, 2020 at 08:34:15AM -0800, Daisuke Nojiri wrote:
> > This patch adds a driver for PCHG (Peripheral CHarGer). PCHG is a
> > framework managing power supplies for peripheral devices.
> > 
> > This driver creates a sysfs node for each peripheral charge port:
> > 
> > 	/sys/class/power_supply/PCHGn
> > 
> > where <n> is the index of a charge port.
> > 
> > For example, when a stylus is connected to a NFC/WLC port, the node
> > prints:
> > 
> > 	/sys/class/power_supply/PCHG0/
> > 		capacity=50
> > 		status=Charging
> > 		type=Wireless
> > 
> > Signed-off-by: Daisuke Nojiri <dnojiri@...omium.org>
> > ---
> > v1 -> v2
> > * Separate mfd/cros_ec_dev.c
> > * Make CONFIG_CHARGER_CROS_PCHG default to CONFIG_MFD_CROS_EC_DEV
> > ---
> > 
> >  drivers/power/supply/Kconfig                  |  10 +
> >  drivers/power/supply/Makefile                 |   1 +
> >  .../power/supply/cros_peripheral_charger.c    | 346 ++++++++++++++++++
> >  .../linux/platform_data/cros_ec_commands.h    |  48 +++
> >  4 files changed, 405 insertions(+)
> >  create mode 100644 drivers/power/supply/cros_peripheral_charger.c
> > 
> > diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> > index eec646c568b7be..407f9fbbc2bb50 100644
> > --- a/drivers/power/supply/Kconfig
> > +++ b/drivers/power/supply/Kconfig
> > @@ -714,6 +714,16 @@ config CHARGER_CROS_USBPD
> >  	  what is connected to USB PD ports from the EC and converts
> >  	  that into power_supply properties.
> >  
> > +config CHARGER_CROS_PCHG
> > +	tristate "ChromeOS EC based peripheral charger"
> > +	depends on MFD_CROS_EC_DEV
> > +	default MFD_CROS_EC_DEV
> > +	help
> > +	  Say Y here to enable ChromeOS EC based peripheral charge driver.
> > +	  This driver gets various information about the devices connected to
> > +	  the peripheral charge ports from the EC and converts that into
> > +	  power_supply properties.
> > +
> >  config CHARGER_SC2731
> >  	tristate "Spreadtrum SC2731 charger driver"
> >  	depends on MFD_SC27XX_PMIC || COMPILE_TEST
> > diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> > index dd4b86318cd9bd..5263472a64809b 100644
> > --- a/drivers/power/supply/Makefile
> > +++ b/drivers/power/supply/Makefile
> > @@ -91,6 +91,7 @@ obj-$(CONFIG_CHARGER_TPS65217)	+= tps65217_charger.o
> >  obj-$(CONFIG_AXP288_FUEL_GAUGE) += axp288_fuel_gauge.o
> >  obj-$(CONFIG_AXP288_CHARGER)	+= axp288_charger.o
> >  obj-$(CONFIG_CHARGER_CROS_USBPD)	+= cros_usbpd-charger.o
> > +obj-$(CONFIG_CHARGER_CROS_PCHG)	+= cros_peripheral_charger.o
> >  obj-$(CONFIG_CHARGER_SC2731)	+= sc2731_charger.o
> >  obj-$(CONFIG_FUEL_GAUGE_SC27XX)	+= sc27xx_fuel_gauge.o
> >  obj-$(CONFIG_CHARGER_UCS1002)	+= ucs1002_power.o
> > diff --git a/drivers/power/supply/cros_peripheral_charger.c b/drivers/power/supply/cros_peripheral_charger.c
> > new file mode 100644
> > index 00000000000000..db68d3b7c80f32
> > --- /dev/null
> > +++ b/drivers/power/supply/cros_peripheral_charger.c
> > @@ -0,0 +1,346 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Power supply driver for ChromeOS EC based Peripheral Device Charger.
> > + *
> > + * Copyright 2020 Google LLC.
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/notifier.h>
> > +#include <linux/platform_data/cros_ec_commands.h>
> > +#include <linux/platform_data/cros_ec_proto.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/power_supply.h>
> > +#include <linux/slab.h>
> > +#include <linux/stringify.h>
> > +#include <linux/types.h>
> > +
> > +#define DRV_NAME		"cros-ec-pchg"
> > +#define PCHG_DIR_NAME		"PCHG%d"
> > +#define PCHG_DIR_NAME_LENGTH	sizeof("PCHG" __stringify(EC_PCHG_MAX_PORTS))
> 
> I think this is way too complex. Just pick a reasonable
> constant, such as 8 or 16.
> 
> > +#define PCHG_CACHE_UPDATE_DELAY	msecs_to_jiffies(500)
> > +
> > +struct port_data {
> > +	int port_number;
> > +	char name[PCHG_DIR_NAME_LENGTH];
> > +	struct power_supply *psy;
> > +	struct power_supply_desc psy_desc;
> > +	int psy_status;
> > +	int battery_percentage;
> > +	struct charger_data *charger;
> > +	unsigned long last_update;
> > +};
> > +
> > +struct charger_data {
> > +	struct device *dev;
> > +	struct cros_ec_dev *ec_dev;
> > +	struct cros_ec_device *ec_device;
> > +	int num_registered_psy;
> > +	struct port_data *ports[EC_PCHG_MAX_PORTS];
> > +	struct notifier_block notifier;
> > +};
> > +
> > +static enum power_supply_property cros_pchg_props[] = {
> > +	POWER_SUPPLY_PROP_STATUS,
> > +	POWER_SUPPLY_PROP_CAPACITY,
> > +	/*
> > +	 * todo: Add the following.
> 
> I would suggest to either implement this or to drop the comment.
> 
> > +	 *
> > +	 * POWER_SUPPLY_PROP_TECHNOLOGY,
> > +	 * POWER_SUPPLY_PROP_ERROR,
> > +	 * POWER_SUPPLY_PROP_SERIAL_NUMBER,
> > +	 *
> > +	 * POWER_SUPPLY_PROP_ONLINE can't be used because it indicates the
> > +	 * system is powered by AC.
> > +	 */
> > +};
> > +
> > +static int cros_pchg_ec_command(const struct charger_data *charger,
> > +				unsigned int version,
> > +				unsigned int command,
> > +				const void *outdata,
> > +				unsigned int outsize,
> > +				void *indata,
> > +				unsigned int insize)
> > +{
> > +	struct cros_ec_dev *ec_dev = charger->ec_dev;
> > +	struct cros_ec_command *msg;
> > +	int ret;
> > +
> > +	msg = kzalloc(sizeof(*msg) + max(outsize, insize), GFP_KERNEL);
> > +	if (!msg)
> > +		return -ENOMEM;
> > +
> > +	msg->version = version;
> > +	msg->command = ec_dev->cmd_offset + command;
> > +	msg->outsize = outsize;
> > +	msg->insize = insize;
> > +
> > +	if (outsize)
> > +		memcpy(msg->data, outdata, outsize);
> > +
> > +	ret = cros_ec_cmd_xfer_status(charger->ec_device, msg);
> > +	if (ret >= 0 && insize)
> > +		memcpy(indata, msg->data, insize);
> > +
> > +	kfree(msg);
> > +	return ret;
> > +}
> > +
> > +static int cros_pchg_port_count(const struct charger_data *charger)
> > +{
> > +	struct ec_response_pchg_count rsp;
> > +	int ret;
> > +
> > +	ret = cros_pchg_ec_command(charger, 0, EC_CMD_PCHG_COUNT,
> > +				   NULL, 0, &rsp, sizeof(rsp));
> > +	if (ret < 0) {
> > +		dev_warn(charger->dev,
> > +			 "Unable to get number or ports (err:%d)\n", ret);
> 
> Why dev_warn() and not dev_err() ?
> 
> > +		return ret;
> > +	}
> > +
> > +	return rsp.port_count;
> > +}
> > +
> > +static int cros_pchg_get_status(struct port_data *port)
> > +{
> > +	struct charger_data *charger = port->charger;
> > +	struct ec_params_pchg req;
> > +	struct ec_response_pchg rsp;
> > +	struct device *dev = charger->dev;
> > +	int ret;
> > +
> > +	req.port = port->port_number;
> > +	ret = cros_pchg_ec_command(charger, 0, EC_CMD_PCHG,
> > +				   &req, sizeof(req), &rsp, sizeof(rsp));
> > +	if (ret < 0) {
> > +		dev_err(dev, "Unable to get port.%d status (err:%d)\n",
> > +			port->port_number, ret);
> > +		return ret;
> > +	}
> > +
> > +	switch (rsp.state) {
> > +	case PCHG_STATE_RESET:
> > +	case PCHG_STATE_INITIALIZED:
> > +	case PCHG_STATE_ENABLED:
> > +	default:
> > +		port->psy_status = POWER_SUPPLY_STATUS_UNKNOWN;
> > +		port->battery_percentage = 0;
> > +		break;
> > +	case PCHG_STATE_DETECTED:
> > +		port->psy_status = POWER_SUPPLY_STATUS_NOT_CHARGING;
> > +		port->battery_percentage = rsp.battery_percentage;
> > +		break;
> > +	case PCHG_STATE_CHARGING:
> > +		port->psy_status = POWER_SUPPLY_STATUS_CHARGING;
> > +		port->battery_percentage = rsp.battery_percentage;
> > +		break;
> > +	}
> > +
> > +	dev_dbg(dev,
> > +		"Port %d: state=%d battery=%d%%\n",
> > +		port->port_number, rsp.state, rsp.battery_percentage);
> > +
> > +	return 0;
> > +}
> > +
> > +static int cros_pchg_get_port_status(struct port_data *port, bool ratelimit)
> > +{
> > +	int ret;
> > +
> > +	if (ratelimit &&
> > +	    time_is_after_jiffies(port->last_update + PCHG_CACHE_UPDATE_DELAY))
> 
> Is this correct, or should it be time_is_before_jiffies() ?
> 
> > +		return 0;
> > +
> > +	ret = cros_pchg_get_status(port);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	port->last_update = jiffies;
> > +
> > +	return ret;
> > +}
> > +
> > +static int cros_pchg_get_prop(struct power_supply *psy,
> > +			      enum power_supply_property psp,
> > +			      union power_supply_propval *val)
> > +{
> > +	struct port_data *port = power_supply_get_drvdata(psy);
> > +
> > +	switch (psp) {
> > +	case POWER_SUPPLY_PROP_STATUS:
> > +	case POWER_SUPPLY_PROP_CAPACITY:
> > +		cros_pchg_get_port_status(port, true);
> > +		break;
> > +	default:
> > +		break;
> > +	}
> 
> Is the above case statement really needed (in other words, will this
> function ever be called for anything but POWER_SUPPLY_PROP_STATUS and
> POWER_SUPPLY_PROP_CAPACITY) ?
> 
> > +
> > +	switch (psp) {
> > +	case POWER_SUPPLY_PROP_STATUS:
> > +		val->intval = port->psy_status;
> > +		break;
> > +	case POWER_SUPPLY_PROP_CAPACITY:
> > +		val->intval = port->battery_percentage;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int cros_pchg_event(const struct charger_data *charger,
> > +			   unsigned long host_event)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < charger->num_registered_psy; i++)
> > +		cros_pchg_get_port_status(charger->ports[i], false);
> > +
> > +	return NOTIFY_OK;
> > +}
> > +
> > +static u32 cros_get_device_event(const struct charger_data *charger)
> > +{
> > +	struct ec_params_device_event req;
> > +	struct ec_response_device_event rsp;
> > +	struct device *dev = charger->dev;
> > +	int ret;
> > +
> > +	req.param = EC_DEVICE_EVENT_PARAM_GET_CURRENT_EVENTS;
> > +	ret = cros_pchg_ec_command(charger, 0, EC_CMD_DEVICE_EVENT,
> > +				   &req, sizeof(req), &rsp, sizeof(rsp));
> > +	if (ret < 0) {
> > +		dev_warn(dev, "Unable to get device events (err:%d)\n", ret);
> > +		return 0;
> > +	}
> > +
> > +	return rsp.event_mask;
> > +}
> > +
> > +static int cros_ec_notify(struct notifier_block *nb,
> > +			  unsigned long queued_during_suspend,
> > +			  void *data)
> > +{
> > +	struct cros_ec_device *ec_dev = (struct cros_ec_device *)data;
> > +	u32 host_event = cros_ec_get_host_event(ec_dev);
> > +	struct charger_data *charger =
> > +			container_of(nb, struct charger_data, notifier);
> > +	u32 device_event_mask;
> > +
> > +	if (!host_event)
> > +		return NOTIFY_BAD;
> > +
> > +	if (!(host_event & EC_HOST_EVENT_MASK(EC_HOST_EVENT_DEVICE)))
> > +		return NOTIFY_DONE;
> > +
> > +	/*
> > +	 * todo: Retrieve device event mask in common place
> > +	 * (e.g. cros_ec_proto.c).
> > +	 */
> > +	device_event_mask = cros_get_device_event(charger);
> > +	if (!(device_event_mask & EC_DEVICE_EVENT_MASK(EC_DEVICE_EVENT_WLC)))
> > +		return NOTIFY_DONE;
> > +
> > +	return cros_pchg_event(charger, host_event);
> > +}
> > +
> > +static int cros_pchg_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct cros_ec_dev *ec_dev = dev_get_drvdata(dev->parent);
> > +	struct cros_ec_device *ec_device = ec_dev->ec_dev;
> > +	struct power_supply_desc *psy_desc;
> > +	struct charger_data *charger;
> > +	struct power_supply *psy;
> > +	struct port_data *port;
> > +	struct notifier_block *nb;
> > +	int num_ports;
> > +	int ret;
> > +	int i;
> > +
> > +	charger = devm_kzalloc(dev, sizeof(*charger), GFP_KERNEL);
> > +	if (!charger)
> > +		return -ENOMEM;
> > +
> > +	charger->dev = dev;
> > +	charger->ec_dev = ec_dev;
> > +	charger->ec_device = ec_device;
> > +
> > +	ret = cros_pchg_port_count(charger);
> > +	if (ret <= 0) {
> > +		/*
> > +		 * This feature is enabled by the EC and the kernel driver is
> > +		 * included by default for CrOS devices. Don't need to be loud
> > +		 * since this error can be normal.
> > +		 */
> > +		dev_info(dev, "No peripheral charge ports (err:%d)\n", ret);
> 
> Is this message really needed / useful ? I am concerned that it will pollute
> lots of logs. Also, cros_pchg_port_count() alreayd displays an error/warning
> message.
> 
> > +		return -ENODEV;
> > +	}
> > +
> > +	num_ports = ret;
> > +	if (num_ports > EC_PCHG_MAX_PORTS) {
> > +		dev_err(dev, "Too many peripheral charge ports (%d)\n",
> > +			num_ports);
> > +		return -ENOBUFS;
> 
> "No buffer space available" ?
> 
> A more dynamic solution would be to allocate 'struct port_data *ports'
> separately and just accept the number of ports.
> 
> > +	}
> > +
> > +	dev_info(dev, "%d peripheral charge ports found\n", num_ports);
> > +
> 
> Personally I think this driver is way too noisy.
> 
> > +	for (i = 0; i < num_ports; i++) {
> > +		struct power_supply_config psy_cfg = {};
> > +
> > +		port = devm_kzalloc(dev, sizeof(*port), GFP_KERNEL);
> > +		if (!port)
> > +			return -ENOMEM;
> > +
> > +		port->charger = charger;
> > +		port->port_number = i;
> > +		snprintf(port->name, sizeof(port->name), PCHG_DIR_NAME, i);
> > +
> > +		psy_desc = &port->psy_desc;
> > +		psy_desc->name = port->name;
> > +		psy_desc->type = POWER_SUPPLY_TYPE_WIRELESS;
> > +		psy_desc->get_property = cros_pchg_get_prop;
> > +		psy_desc->external_power_changed = NULL;
> > +		psy_desc->properties = cros_pchg_props;
> > +		psy_desc->num_properties = ARRAY_SIZE(cros_pchg_props);
> > +		psy_cfg.drv_data = port;
> > +
> > +		psy = devm_power_supply_register_no_ws(dev, psy_desc, &psy_cfg);
> > +		if (IS_ERR(psy)) {
> > +			dev_err(dev, "Failed to register power supply\n");
> 
> Is this an "acceptable" or ignorable error ? It seems to be somewhat odd.
> 
> > +			continue;
> > +		}
> > +		port->psy = psy;
> > +
> > +		charger->ports[charger->num_registered_psy++] = port;
> > +	}
> > +
> > +	if (!charger->num_registered_psy)
> > +		return -ENODEV;
> > +
> > +	nb = &charger->notifier;
> > +	nb->notifier_call = cros_ec_notify;
> > +	ret = blocking_notifier_chain_register(&ec_dev->ec_dev->event_notifier,
> > +					       nb);
> > +	if (ret < 0)
> > +		dev_err(dev, "Failed to register notifier (err:%d)\n", ret);
> 
> If this is an error, it should be reported to the caller. If it isn't,
> it should not be reported as error.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static struct platform_driver cros_pchg_driver = {
> > +	.driver = {
> > +		.name = DRV_NAME,
> > +	},
> > +	.probe = cros_pchg_probe
> > +};
> > +
> > +module_platform_driver(cros_pchg_driver);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_DESCRIPTION("ChromeOS EC peripheral device charger");
> > +MODULE_ALIAS("platform:" DRV_NAME);
> > diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
> 
> This should be done in a separate patch, and probably simply align
> the current version of cros_ec_commands.h with the version in the
> EC code base (to avoid deviation from that version). We had major
> problems with that earlier, and I am not looking forward to
> re-introducing it.
> 
> > index 58495127dfa656..c0f0a032c8beb6 100644
> > --- a/include/linux/platform_data/cros_ec_commands.h
> > +++ b/include/linux/platform_data/cros_ec_commands.h
> > @@ -4225,6 +4225,7 @@ enum ec_device_event {
> >  	EC_DEVICE_EVENT_TRACKPAD,
> >  	EC_DEVICE_EVENT_DSP,
> >  	EC_DEVICE_EVENT_WIFI,
> > +	EC_DEVICE_EVENT_WLC,
> >  };
> >  
> >  enum ec_device_event_param {
> > @@ -5456,6 +5457,53 @@ struct ec_response_rollback_info {
> >  /* Issue AP reset */
> >  #define EC_CMD_AP_RESET 0x0125
> >  
> > +/**
> > + * Get the number of peripheral charge ports
> > + */
> > +#define EC_CMD_PCHG_COUNT 0x0134
> > +
> > +#define EC_PCHG_MAX_PORTS 8
> > +
> > +struct ec_response_pchg_count {
> > +	uint8_t port_count;
> > +} __ec_align1;
> > +
> > +/**
> > + * Get the status of a peripheral charge port
> > + */
> > +#define EC_CMD_PCHG 0x0135
> > +
> > +struct ec_params_pchg {
> > +	uint8_t port;
> > +} __ec_align1;
> > +
> > +struct ec_response_pchg {
> > +	uint32_t error; /* enum pchg_error */
> > +	uint8_t state; /* enum pchg_state state */
> > +	uint8_t battery_percentage;
> > +} __ec_align2;
> > +
> > +enum pchg_state {
> > +	/* Charger is reset and not initialized. */
> > +	PCHG_STATE_RESET = 0,
> > +	/* Charger is initialized or disabled. */
> > +	PCHG_STATE_INITIALIZED,
> > +	/* Charger is enabled and ready to detect a device. */
> > +	PCHG_STATE_ENABLED,
> > +	/* Device is detected in proximity. */
> > +	PCHG_STATE_DETECTED,
> > +	/* Device is being charged. */
> > +	PCHG_STATE_CHARGING,
> > +};
> > +
> > +#define EC_PCHG_STATE_TEXT { \
> > +	[PCHG_STATE_RESET] = "RESET", \
> > +	[PCHG_STATE_INITIALIZED] = "INITIALIZED", \
> > +	[PCHG_STATE_ENABLED] = "ENABLED", \
> > +	[PCHG_STATE_DETECTED] = "DETECTED", \
> > +	[PCHG_STATE_CHARGING] = "CHARGING", \
> > +	}
> > +
> >  /*****************************************************************************/
> >  /* Locate peripheral chips
> >   *

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