Re: [PATCH 2/2] power: supply: cros: allow to set input voltage and current limit.

From: Guenter Roeck
Date: Wed Nov 21 2018 - 14:03:53 EST

Trying again, this time (hopefully if gmail lets me) in plaintext
mode. Sorry for the noise.

On Wed, Nov 21, 2018 at 7:34 AM Enric Balletbo i Serra
<enric.balletbo@xxxxxxxxxxxxx> wrote:
>
> This patch allows reading and writing the input voltage and current
> limit through the POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT and
> POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT sysfs properties. This allows
> userspace to see current values and to re-configure these values at
> runtime based on system-level knowledge or user input.
>
> By default there is no limit, this is reported as a -1 when reading from
> userspace. Writing a value will set the current or voltage limit in uA
> or uV, and writing any negative value will remove that limit.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> ---
>
> drivers/power/supply/cros_usbpd-charger.c | 117 ++++++++++++++++++++++
> 1 file changed, 117 insertions(+)
>
> diff --git a/drivers/power/supply/cros_usbpd-charger.c b/drivers/power/supply/cros_usbpd-charger.c
> index 7e9c3984ef6a..f011ce71b30c 100644
> --- a/drivers/power/supply/cros_usbpd-charger.c
> +++ b/drivers/power/supply/cros_usbpd-charger.c
> @@ -53,6 +53,8 @@ struct charger_data {
> };
>
> static enum power_supply_property cros_usbpd_charger_props[] = {
> + POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT,
> + POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT,
> POWER_SUPPLY_PROP_ONLINE,
> POWER_SUPPLY_PROP_STATUS,
> POWER_SUPPLY_PROP_CURRENT_MAX,
> @@ -80,6 +82,10 @@ static enum power_supply_usb_type cros_usbpd_charger_usb_types[] = {
> POWER_SUPPLY_USB_TYPE_APPLE_BRICK_ID
> };
>
> +/* Input voltage/current limit in mV/mA. Default to none. */
> +static u16 input_voltage_limit = EC_POWER_LIMIT_NONE;
> +static u16 input_current_limit = EC_POWER_LIMIT_NONE;
> +
> static bool cros_usbpd_charger_port_is_dedicated(struct port_data *port)
> {
> return port->port_number >= port->charger->num_usbpd_ports;
> @@ -324,6 +330,26 @@ static int cros_usbpd_charger_get_port_status(struct port_data *port,
> return ret;
> }
>
> +static int cros_usbpd_charger_set_ext_power_limit(struct charger_data *charger,
> + u16 current_lim,
> + u16 voltage_lim)
> +{
> + struct ec_params_external_power_limit_v1 req;
> + int ret;
> +
> + req.current_lim = current_lim;
> + req.voltage_lim = voltage_lim;
> +
> + ret = cros_usbpd_charger_ec_command(charger, 0,
> + EC_CMD_EXTERNAL_POWER_LIMIT,
> + &req, sizeof(req), NULL, 0);
> + if (ret < 0)
> + dev_err(charger->dev,
> + "Unable to set the 'External Power Limit': %d\n", ret);
> +
> + return ret;
> +}
> +
> static void cros_usbpd_charger_power_changed(struct power_supply *psy)
> {
> struct port_data *port = power_supply_get_drvdata(psy);
> @@ -396,6 +422,18 @@ static int cros_usbpd_charger_get_prop(struct power_supply *psy,
> case POWER_SUPPLY_PROP_USB_TYPE:
> val->intval = port->psy_usb_type;
> break;
> + case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> + if (input_current_limit == EC_POWER_LIMIT_NONE)
> + val->intval = -1;
> + else
> + val->intval = input_current_limit * 1000;
> + break;
> + case POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT:
> + if (input_voltage_limit == EC_POWER_LIMIT_NONE)
> + val->intval = -1;
> + else
> + val->intval = input_voltage_limit * 1000;
> + break;
> case POWER_SUPPLY_PROP_MODEL_NAME:
> val->strval = port->model_name;
> break;
> @@ -409,6 +447,82 @@ static int cros_usbpd_charger_get_prop(struct power_supply *psy,
> return 0;
> }
>
> +static int cros_usbpd_charger_set_prop(struct power_supply *psy,
> + enum power_supply_property psp,
> + const union power_supply_propval *val)
> +{
> + struct port_data *port = power_supply_get_drvdata(psy);
> + struct charger_data *charger = port->charger;
> + struct device *dev = charger->dev;
> + u16 intval;
> + int ret;
> +
> + /* U16_MAX in mV/mA is the maximum supported value */
> + if (val->intval > U16_MAX * 1000)

The accepted upper limit is 0xffff * 1000, so this can result in an
intval of 0xffff after the divide
operation below. At the same time, EC_POWER_LIMIT_NONE is defined as
0xffff. This means
that setting a value of 65535000 will be interpreted as
EC_POWER_LIMIT_NONE and, when
read, will return -1. This is undesirable, but easy to fix by making
the above check ">="
instead of ">".

> + return -EINVAL;
> + else if (val->intval < 0)

Unnecessary else

> + /* A negative number is used to clear the limit */
> + intval = EC_POWER_LIMIT_NONE;
> + else
> + /* Convert from uA/uV to mA/mV */
> + intval = val->intval / 1000;
> +
> + switch (psp) {
> + case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> + ret = cros_usbpd_charger_set_ext_power_limit(charger, intval,
> + input_voltage_limit);
> + if (ret < 0)
> + break;
> +
> + input_current_limit = intval;
> + if (input_current_limit == EC_POWER_LIMIT_NONE)
> + dev_info(dev,
> + "External Current Limit cleared for all ports\n");
> + else
> + dev_info(dev,
> + "External Current Limit set to %dmA for all ports\n",
> + input_current_limit);
> + break;
> + case POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT:
> + ret = cros_usbpd_charger_set_ext_power_limit(charger,
> + input_current_limit,
> + intval);
> + if (ret < 0)
> + break;
> +
> + input_voltage_limit = intval;
> + if (input_voltage_limit == EC_POWER_LIMIT_NONE)
> + dev_info(dev,
> + "External Voltage Limit cleared for all ports\n");
> + else
> + dev_info(dev,
> + "External Voltage Limit set to %dmV for all ports\n",
> + input_voltage_limit);
> + break;
> + default:
> + ret = -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +static int cros_usbpd_charger_property_is_writeable(struct power_supply *psy,
> + enum power_supply_property psp)
> +{
> + int ret;
> +
> + switch (psp) {
> + case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> + case POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT:
> + ret = 1;
> + break;
> + default:
> + ret = 0;
> + }
> +
> + return ret;
> +}
> +
> static int cros_usbpd_charger_ec_event(struct notifier_block *nb,
> unsigned long queued_during_suspend,
> void *_notify)
> @@ -525,6 +639,9 @@ static int cros_usbpd_charger_probe(struct platform_device *pd)
>
> psy_desc = &port->psy_desc;
> psy_desc->get_property = cros_usbpd_charger_get_prop;
> + psy_desc->set_property = cros_usbpd_charger_set_prop;
> + psy_desc->property_is_writeable =
> + cros_usbpd_charger_property_is_writeable;
> psy_desc->external_power_changed =
> cros_usbpd_charger_power_changed;
> psy_cfg.drv_data = port;
> --
> 2.19.1
>