linux-kernel - Re: [PATCH v2 3/3] usb: typec: tcpm: add get max power support

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Message-ID: <19b39d82-8510-2717-cf3b-71cb955373d0@rock-chips.com>
Date:   Tue, 21 Mar 2023 09:32:53 +0800
From:   Frank Wang <frank.wang@...k-chips.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     linux@...ck-us.net, heikki.krogerus@...ux.intel.com,
        gregkh@...uxfoundation.org, heiko@...ech.de,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, huangtao@...k-chips.com,
        william.wu@...k-chips.com, jianwei.zheng@...k-chips.com,
        yubing.zhang@...k-chips.com, wmc@...k-chips.com
Subject: Re: [PATCH v2 3/3] usb: typec: tcpm: add get max power support

Hi Sebastian,

On 2023/3/21 4:31, Sebastian Reichel wrote:
> Hi,
>
> On Mon, Mar 20, 2023 at 06:07:11PM +0800, Frank Wang wrote:
>> Traverse fixed pdos to calculate the maximum power that the charger
>> can provide, and it can be get by POWER_SUPPLY_PROP_INPUT_POWER_LIMIT
>> property.
>>
>> Signed-off-by: Frank Wang <frank.wang@...k-chips.com>
>> ---
>>   drivers/usb/typec/tcpm/tcpm.c | 24 ++++++++++++++++++++++++
>>   1 file changed, 24 insertions(+)
>>
>> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
>> index 13830b5e2d09f..d6ad3cdf9e4af 100644
>> --- a/drivers/usb/typec/tcpm/tcpm.c
>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>> @@ -6320,6 +6320,27 @@ static int tcpm_psy_get_current_now(struct tcpm_port *port,
>>   	return 0;
>>   }
>>   
>> +static int tcpm_psy_get_input_power_limit(struct tcpm_port *port,
>> +					  union power_supply_propval *val)
>> +{
>> +	unsigned int src_mv, src_ma, max_src_mw = 0;
>> +	unsigned int i, tmp;
>> +
>> +	for (i = 0; i < port->nr_source_caps; i++) {
>> +		u32 pdo = port->source_caps[i];
>> +
>> +		if (pdo_type(pdo) == PDO_TYPE_FIXED) {
>> +			src_mv = pdo_fixed_voltage(pdo);
>> +			src_ma = pdo_max_current(pdo);
>> +			tmp = src_mv * src_ma / 1000;
>> +			max_src_mw = tmp > max_src_mw ? tmp : max_src_mw;
>> +		}
>> +	}
>> +
>> +	val->intval = max_src_mw;
> The power-supply subsystem expects Microwatts and not Milliwatts.

Yes, but I see the 'power_supply_propval' member 'intval' is an integer 
type, I worry about it may be overflowed that uses Microwatts.


BR.
Frank

> -- Sebastian
>
>> +	return 0;
>> +}
>> +
>>   static int tcpm_psy_get_prop(struct power_supply *psy,
>>   			     enum power_supply_property psp,
>>   			     union power_supply_propval *val)
>> @@ -6349,6 +6370,9 @@ static int tcpm_psy_get_prop(struct power_supply *psy,
>>   	case POWER_SUPPLY_PROP_CURRENT_NOW:
>>   		ret = tcpm_psy_get_current_now(port, val);
>>   		break;
>> +	case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
>> +		tcpm_psy_get_input_power_limit(port, val);
>> +		break;
>>   	default:
>>   		ret = -EINVAL;
>>   		break;
>> -- 
>> 2.17.1
>>