Re: [External] [PATCH 3/4] platform/x86: thinkpad_acpi: support force-discharge

[Mark Pearson]

Hi Thomas,

On 2021-11-13 05:42, Thomas Weißschuh wrote:
> This adds support for the force-discharge charge_behaviour through the
> embedded controller of ThinkPads.
> 
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> 
> ---
> 
> This patch is based on https://lore.kernel.org/platform-driver-x86/c2504700-06e9-e7d8-80f7-de90b0b6dfb5@xxxxxxxxx/>> ---
>  drivers/platform/x86/thinkpad_acpi.c | 103 +++++++++++++++++++++++++--
>  1 file changed, 99 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index 9c632df734bb..e8c98e9aff71 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -9319,6 +9319,8 @@ static struct ibm_struct mute_led_driver_data = {
>  #define SET_START	"BCCS"
>  #define GET_STOP	"BCSG"
>  #define SET_STOP	"BCSS"
> +#define GET_DISCHARGE	"BDSG"
> +#define SET_DISCHARGE	"BDSS"
>  
>  enum {
>  	BAT_ANY = 0,
> @@ -9335,6 +9337,7 @@ enum {
>  	/* This is used in the get/set helpers */
>  	THRESHOLD_START,
>  	THRESHOLD_STOP,
> +	FORCE_DISCHARGE,
>  };
>  
>  struct tpacpi_battery_data {
> @@ -9342,6 +9345,7 @@ struct tpacpi_battery_data {
>  	int start_support;
>  	int charge_stop;
>  	int stop_support;
> +	unsigned int charge_behaviours;
>  };
>  
>  struct tpacpi_battery_driver_data {
> @@ -9399,6 +9403,12 @@ static int tpacpi_battery_get(int what, int battery, int *ret)
>  		if (*ret == 0)
>  			*ret = 100;
>  		return 0;
> +	case FORCE_DISCHARGE:
> +		if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, ret, battery))
> +			return -ENODEV;
> +		/* The force discharge status is in bit 0 */
> +		*ret = *ret & 0x01;
> +		return 0;
>  	default:
>  		pr_crit("wrong parameter: %d", what);
>  		return -EINVAL;
> @@ -9427,6 +9437,16 @@ static int tpacpi_battery_set(int what, int battery, int value)
>  			return -ENODEV;
>  		}
>  		return 0;
> +	case FORCE_DISCHARGE:
> +		/* Force discharge is in bit 0,
> +		 * break on AC attach is in bit 1 (won't work on some ThinkPads),
> +		 * battery ID is in bits 8-9, 2 bits.
> +		 */
> +		if (ACPI_FAILURE(tpacpi_battery_acpi_eval(SET_DISCHARGE, &ret, param))) {
> +			pr_err("failed to set force dischrage on %d", battery);
> +			return -ENODEV;
> +		}
> +		return 0;
>  	default:
>  		pr_crit("wrong parameter: %d", what);
>  		return -EINVAL;
> @@ -9445,6 +9465,8 @@ static int tpacpi_battery_probe(int battery)
>  	 * 2) Check for support
>  	 * 3) Get the current stop threshold
>  	 * 4) Check for support
> +	 * 5) Get the current force discharge status
> +	 * 6) Check for support
>  	 */
>  	if (acpi_has_method(hkey_handle, GET_START)) {
>  		if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_START, &ret, battery)) {
> @@ -9481,10 +9503,25 @@ static int tpacpi_battery_probe(int battery)
>  			return -ENODEV;
>  		}
>  	}
> -	pr_info("battery %d registered (start %d, stop %d)",
> -			battery,
> -			battery_info.batteries[battery].charge_start,
> -			battery_info.batteries[battery].charge_stop);
> +	if (acpi_has_method(hkey_handle, GET_DISCHARGE)) {
> +		if (ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_DISCHARGE, &ret, battery))) {
> +			pr_err("Error probing battery discharge; %d\n", battery);
> +			return -ENODEV;
> +		}
> +		/* Support is marked in bit 8 */
> +		if (ret & BIT(8))
> +			battery_info.batteries[battery].charge_behaviours |=
> +				BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE);
> +	}
> +
> +	battery_info.batteries[battery].charge_behaviours |=
> +		BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO);
> +
> +	pr_info("battery %d registered (start %d, stop %d, behaviours: 0x%x)\n",
> +		battery,
> +		battery_info.batteries[battery].charge_start,
> +		battery_info.batteries[battery].charge_stop,
> +		battery_info.batteries[battery].charge_behaviours);
>  
>  	return 0;
>  }
> @@ -9619,6 +9656,28 @@ static ssize_t charge_control_end_threshold_show(struct device *device,
>  	return tpacpi_battery_show(THRESHOLD_STOP, device, buf);
>  }
>  
> +static ssize_t charge_behaviour_show(struct device *dev,
> +				     struct device_attribute *attr,
> +				     char *buf)
> +{
> +	enum power_supply_charge_behaviour active = POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO;
> +	struct power_supply *supply = to_power_supply(dev);
> +	unsigned int available;
> +	int ret, battery;
> +
> +	battery = tpacpi_battery_get_id(supply->desc->name);
> +	available = battery_info.batteries[battery].charge_behaviours;
> +
> +	if (available & BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE)) {
> +		if (tpacpi_battery_get(FORCE_DISCHARGE, battery, &ret))
> +			return -ENODEV;
> +		if (ret)
> +			active = POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE;
> +	}
> +
> +	return power_supply_charge_behaviour_show(dev, available, active, buf);
> +}
> +
>  static ssize_t charge_control_start_threshold_store(struct device *dev,
>  				struct device_attribute *attr,
>  				const char *buf, size_t count)
> @@ -9633,8 +9692,43 @@ static ssize_t charge_control_end_threshold_store(struct device *dev,
>  	return tpacpi_battery_store(THRESHOLD_STOP, dev, buf, count);
>  }
>  
> +static ssize_t charge_behaviour_store(struct device *dev,
> +				      struct device_attribute *attr,
> +				      const char *buf, size_t count)
> +{
> +	struct power_supply *supply = to_power_supply(dev);
> +	int selected, battery, ret;
> +	unsigned int available;
> +
> +	battery = tpacpi_battery_get_id(supply->desc->name);
> +	available = battery_info.batteries[battery].charge_behaviours;
> +	selected = power_supply_charge_behaviour_parse(available, buf);
> +
> +	if (selected < 0)
> +		return selected;
> +
> +	switch (selected) {
> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
> +		ret = tpacpi_battery_set(FORCE_DISCHARGE, battery, 0);
> +		if (ret < 0)
> +			return ret;
> +		break;
> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
> +		ret = tpacpi_battery_set(FORCE_DISCHARGE, battery, 1);
> +		if (ret < 0)
> +			return ret;
> +		break;
> +	default:
> +		dev_err(dev, "Unexpected charge behaviour: %d\n", selected);
> +		return -EINVAL;
> +	}
> +
> +	return count;
> +}
> +
>  static DEVICE_ATTR_RW(charge_control_start_threshold);
>  static DEVICE_ATTR_RW(charge_control_end_threshold);
> +static DEVICE_ATTR_RW(charge_behaviour);
>  static struct device_attribute dev_attr_charge_start_threshold = __ATTR(
>  	charge_start_threshold,
>  	0644,
> @@ -9653,6 +9747,7 @@ static struct attribute *tpacpi_battery_attrs[] = {
>  	&dev_attr_charge_control_end_threshold.attr,
>  	&dev_attr_charge_start_threshold.attr,
>  	&dev_attr_charge_stop_threshold.attr,
> +	&dev_attr_charge_behaviour.attr,
>  	NULL,
>  };
>  
> 
Sorry for the slow review - been busy this week. Thank you for
implementing this - it's great to be getting this into the kernel and
it's something we have had on our todo list for a little while now.

I can confirm the BDSG and BDSS APIs are correct along with the bit
field defines you have used. Not sure if that's helpful but as I have
access to some internal documents I figured I'd check :)

I'll note that bit 10 in BDSG should flag if the 'enable breaking by AC
detaching' feature is supported. You're not using it so I don't think
that's important - but figured I'd mention it because of the comment
that not all thinkpads support it.

Mark