linux-kernel - Re: [RFC] Limiting charge current on Droid 4 (and N900)

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Date:   Sat, 27 Jun 2020 13:01:53 +0200
From:   Merlijn Wajer <merlijn@...zup.org>
To:     Pavel Machek <pavel@....cz>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, tony@...mide.com, sre@...nel.org,
        nekit1000@...il.com, mpartap@....net, martin_rysavy@...trum.cz,
        linux-pm@...r.kernel.org
Subject: Re: [RFC] Limiting charge current on Droid 4 (and N900)

Hi Pavel,

On 15/06/2020 16:05, Pavel Machek wrote:
> Hi!
> 
> Droid 4 has same problem as N900: it is often neccessary to manually
> tweak current draw from USB, for example when using thin charging cable.
> 
> N900 creates unique attribute by hand, but I believe
> POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT looks suitable. (Should N900 be
> converted?)
> 
> Comments? Would the patch be acceptable after fixing whitespace?

I'm not very knowledgeable on batteries - but the patch looks good to me.

Could you perhaps explain what exactly this fixes? I've seen some
interesting behaviour when plugging a Droid 4 into a PC (or wall
charger, really): the led blinks for a few seconds until it stabilises.

And then there's the issue where, once the battery is full, it will
switch between charging and discharging every few seconds/minutes.

Cheers,
Merlijn

> 
> Best regards,
> 									Pavel
> 
> Signed-off-by: Pavel Machek <pavel@....cz>
> 
> diff --git a/drivers/power/supply/cpcap-battery.c b/drivers/power/supply/cpcap-battery.c
> index b16848cfb58c..39a00716372f 100644
> --- a/drivers/power/supply/cpcap-battery.c
> +++ b/drivers/power/supply/cpcap-battery.c
> @@ -3,7 +3,7 @@
>   *
>   * Copyright (C) 2017 Tony Lindgren <tony@...mide.com>
>   *
> - * Some parts of the code based on earlie Motorola mapphone Linux kernel
> + * Some parts of the code based on earlier Motorola mapphone Linux kernel
>   * drivers:
>   *
>   * Copyright (C) 2009-2010 Motorola, Inc.
> diff --git a/drivers/power/supply/cpcap-charger.c b/drivers/power/supply/cpcap-charger.c
> index cf1e05b511d9..292d7a31c663 100644
> --- a/drivers/power/supply/cpcap-charger.c
> +++ b/drivers/power/supply/cpcap-charger.c
> @@ -89,6 +89,8 @@
>   * CPCAP_REG_CRM charge currents. These seem to match MC13783UG.pdf
>   * values in "Table 8-3. Charge Path Regulator Current Limit
>   * Characteristics" for the nominal values.
> + *
> + * Except 70mA and 1.596A and unlimited, these are simply 88.7mA / step.
>   */
>  #define CPCAP_REG_CRM_ICHRG(val)	(((val) & 0xf) << 0)
>  #define CPCAP_REG_CRM_ICHRG_0A000	CPCAP_REG_CRM_ICHRG(0x0)
> @@ -147,6 +149,8 @@ struct cpcap_charger_ddata {
>  	int status;
>  	int state;
>  	int voltage;
> +	int limit_current;
> +
>  	int last_current;
>  	int last_current_retries;
>  };
> @@ -175,6 +179,7 @@ static enum power_supply_property cpcap_charger_props[] = {
>  	POWER_SUPPLY_PROP_STATUS,
>  	POWER_SUPPLY_PROP_ONLINE,
>  	POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE,
> +	POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT,
>  	POWER_SUPPLY_PROP_VOLTAGE_NOW,
>  	POWER_SUPPLY_PROP_CURRENT_NOW,
>  };
> @@ -238,6 +243,9 @@ static int cpcap_charger_get_property(struct power_supply *psy,
>  	case POWER_SUPPLY_PROP_STATUS:
>  		val->intval = ddata->status;
>  		break;
> +  	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> +		val->intval = ddata->limit_current;
> +		break;
>  	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
>  		val->intval = ddata->voltage;
>  		break;
> @@ -308,6 +316,25 @@ cpcap_charger_get_bat_const_charge_voltage(struct cpcap_charger_ddata *ddata)
>  	return voltage;
>  }
>  
> +static int cpcap_charger_current_to_regval(int microamp)
> +{
> +	int miliamp = microamp/1000;
> +	int res;
> +	if (miliamp < 0)
> +		return -EINVAL;
> +	if (miliamp < 70)
> +		return CPCAP_REG_CRM_ICHRG(0x0);
> +	if (miliamp < 177)
> +		return CPCAP_REG_CRM_ICHRG(0x1);
> +	if (miliamp > 1596)
> +		return CPCAP_REG_CRM_ICHRG(0xe);
> +
> +	res = microamp / 88666;
> +	if (res > 0xd)
> +		res = 0xd;
> +	return CPCAP_REG_CRM_ICHRG(res);
> +}
> +
>  static int cpcap_charger_set_property(struct power_supply *psy,
>  				      enum power_supply_property psp,
>  				      const union power_supply_propval *val)
> @@ -316,6 +343,12 @@ static int cpcap_charger_set_property(struct power_supply *psy,
>  	int voltage, batvolt;
>  
>  	switch (psp) {
> +  	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> +		if (cpcap_charger_current_to_regval(val->intval) < 0)
> +			return -EINVAL;
> +		ddata->limit_current = val->intval;
> +		schedule_delayed_work(&ddata->detect_work, 0);
> +		break;
>  	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
>  		voltage = cpcap_charger_match_voltage(val->intval);
>  		batvolt = cpcap_charger_get_bat_const_charge_voltage(ddata);
> @@ -335,6 +368,7 @@ static int cpcap_charger_property_is_writeable(struct power_supply *psy,
>  					       enum power_supply_property psp)
>  {
>  	switch (psp) {
> +	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
>  	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
>  		return 1;
>  	default:
> @@ -657,23 +691,21 @@ static void cpcap_usb_detect(struct work_struct *work)
>  
>  	if (!ddata->feeding_vbus && cpcap_charger_vbus_valid(ddata) &&
>  	    s.chrgcurr1) {
> -		int max_current;
> -		int vchrg;
> +		int max_current = 532000;
> +		int vchrg, ichrg;
>  
>  		if (cpcap_charger_battery_found(ddata))
> -			max_current = CPCAP_REG_CRM_ICHRG_1A596;
> -		else
> -			max_current = CPCAP_REG_CRM_ICHRG_0A532;
> +			max_current = 1596000;
>  
>  		switch (ddata->state) {
>  		case CPCAP_CHARGER_DETECTING:
>  			ddata->last_current_retries = 0;
>  			break;
>  		case CPCAP_CHARGER_DISCONNECTED:
> -			if (ddata->last_current > CPCAP_REG_CRM_ICHRG_0A532) {
> +			if (ddata->last_current > 532000) {
>  				/* Attempt current 3 times before lowering */
>  				if (ddata->last_current_retries++ >= 3) {
> -					ddata->last_current--;
> +					ddata->last_current -= 100000;
>  					ddata->last_current_retries = 0;
>  					/* Wait a bit for voltage to ramp up */
>  					usleep_range(40000, 50000);
> @@ -688,11 +720,16 @@ static void cpcap_usb_detect(struct work_struct *work)
>  			break;
>  		}
>  
> +		if (max_current > ddata->limit_current)
> +			max_current = ddata->limit_current;
> +
>  		ddata->last_current = max_current;
> +
> +		ichrg = cpcap_charger_current_to_regval(max_current);
>  		vchrg = cpcap_charger_voltage_to_regval(ddata->voltage);
>  		error = cpcap_charger_set_state(ddata,
>  						CPCAP_REG_CRM_VCHRG(vchrg),
> -						max_current, 0);
> +						ichrg, 0);
>  		if (error)
>  			goto out_err;
>  		cpcap_charger_update_state(ddata, CPCAP_CHARGER_CHARGING);
> @@ -864,6 +901,7 @@ static int cpcap_charger_probe(struct platform_device *pdev)
>  
>  	ddata->dev = &pdev->dev;
>  	ddata->voltage = 4200000;
> +	ddata->limit_current = 532000;
>  
>  	ddata->reg = dev_get_regmap(ddata->dev->parent, NULL);
>  	if (!ddata->reg)
> 




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