Re: [PATCH v2 10/20] power: supply: bq25890: Add bq25890_set_otg_cfg() helper

[Hans de Goede]

Hi Yauhen,

On 11/15/21 11:11, Yauhen Kharuzhy wrote:
> On Sun, Nov 14, 2021 at 06:03:25PM +0100, Hans de Goede wrote:
>> Add a bq25890_set_otg_cfg() helper function, this is a preparation
>> patch for adding regulator support.
>>
>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
>> ---
>>  drivers/power/supply/bq25890_charger.c | 28 ++++++++++++++------------
>>  1 file changed, 15 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/power/supply/bq25890_charger.c b/drivers/power/supply/bq25890_charger.c
>> index 2bdfb58cda75..3c41fe86b3d3 100644
>> --- a/drivers/power/supply/bq25890_charger.c
>> +++ b/drivers/power/supply/bq25890_charger.c
>> @@ -801,6 +801,17 @@ static int bq25890_power_supply_init(struct bq25890_device *bq)
>>  	return PTR_ERR_OR_ZERO(bq->charger);
>>  }
>>  
>> +static int bq25890_set_otg_cfg(struct bq25890_device *bq, u8 val)
>> +{
>> +	int ret;
>> +
>> +	ret = bq25890_field_write(bq, F_OTG_CFG, val);
>> +	if (ret < 0)
>> +		dev_err(bq->dev, "Error switching to boost/charger mode: %d\n", ret);
> 
> Just a note: if a connected USB device has relative big capacitor
> at power wires inside, then a starting current pulse may be enough to
> overload the boost reguator and VBUS will not be powered. I met this
> at Yoga Book: the firmware set boost current limit to 1.4 A (default
> value for bq25892) but when USB hub connected, the BOOST_FAULT event
> appeared.
> 
> To avoid this, Lenovo uses following trick in its kernel: set a boost
> current limit to big value (2.1 A), wait some time (500 ms) and set
> the current limit to right value (1.4A). This provides enough current to
> charge capacitors in the connected device but saves desired long-time limit
> to prevent overloading if the device consumes too much power itself.

Right I saw this in your git repo, but I cannot reproduce the issue (1)
I was hoping that since you can reproduce this, that you can rebase
your fix on top of my patch-set ?

Also I'm wondering if this behavior should be the default, I believe
that the max. boost current may also be dependent on some external
factors, so maybe we should make this behavior conditional on a
new device-property ?

Regards,

Hans



1) I must admit I did not try really hard, I guess I could try an
USB powered hdd enclosure with a spinning disk

What device are you seeing this with?