linux-kernel - Re: [PATCH v2] rtc: rv3028: Improve trickle charger logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Thu, 22 Jun 2023 10:09:17 +0200
From:   Andrej Picej <andrej.picej@...ik.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     a.zummo@...ertech.it, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, upstream@...tec.de
Subject: Re: [PATCH v2] rtc: rv3028: Improve trickle charger logic

Hi Alexandre,

On 22. 06. 23 09:34, Alexandre Belloni wrote:
> On 22/06/2023 09:16:09+0200, Andrej Picej wrote:
>> Property "trickle-resistor-ohms" allows us to set trickle charger
>> resistor. However there is no possibility to disable it afterwards.
>>
>>  From now on, disable trickle charger circuit in case device-tree
>> property "trickle-resistor-ohms" is set to -1.
>>
>> Additionally, lets make sure we only update internal EEPROM in case of a
>> change. This prevents wear due to excessive EEPROM writes on each probe.
>>
>> Signed-off-by: Andrej Picej <andrej.picej@...ik.com>
>> ---
>> Changes in v2:
>> - disable trickle charger if device tree property trickle-resistor-ohms
>>    is set to -1.
> 
> What about using aux-voltage-chargeable which is the generic property
> for this?

I thought that this is more of a property for specifying if connected 
battery/supercap has charging capabilities. I guess at the end it would 
be the same thing as knowingly disabling the trickle charger even if 
battery/supercap can be charged.
Do you want that I change and use "aux-voltage-chargeable"?

BR,
Andrej

> 
>> ---
>>   drivers/rtc/rtc-rv3028.c | 45 +++++++++++++++++++++++++++++-----------
>>   1 file changed, 33 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/rtc/rtc-rv3028.c b/drivers/rtc/rtc-rv3028.c
>> index ec5d7a614e2d..da2ae81fe7c8 100644
>> --- a/drivers/rtc/rtc-rv3028.c
>> +++ b/drivers/rtc/rtc-rv3028.c
>> @@ -859,7 +859,8 @@ static int rv3028_probe(struct i2c_client *client)
>>   {
>>   	struct rv3028_data *rv3028;
>>   	int ret, status;
>> -	u32 ohms;
>> +	s32 ohms;
>> +	int val_old, val;
>>   	struct nvmem_config nvmem_cfg = {
>>   		.name = "rv3028_nvram",
>>   		.word_size = 1,
>> @@ -937,22 +938,42 @@ static int rv3028_probe(struct i2c_client *client)
>>   	if (ret)
>>   		return ret;
>>   
>> -	/* setup trickle charger */
>> -	if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
>> -				      &ohms)) {
>> -		int i;
>> +	ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &val_old);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	/* mask out only trickle charger bits */
>> +	val_old = val_old & (RV3028_BACKUP_TCE | RV3028_BACKUP_TCR_MASK);
>>   
>> -		for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
>> -			if (ohms == rv3028_trickle_resistors[i])
>> -				break;
>> +	/* setup trickle charger */
>> +	if (!of_property_read_s32(client->dev.of_node, "trickle-resistor-ohms",
>> +				  &ohms)) {
>> +		/* disable trickle charger if trickle-resistor-ohms = <(-1)>; */
>> +		if (ohms == -1) {
>> +			val = val_old & ~RV3028_BACKUP_TCE;
>> +		} else {
>> +			int i;
>> +
>> +			for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
>> +				if (ohms == rv3028_trickle_resistors[i])
>> +					break;
>> +
>> +			if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
>> +				/* enable trickle charger and its resistor */
>> +				val = RV3028_BACKUP_TCE | i;
>> +			} else {
>> +				dev_warn(&client->dev, "invalid trickle resistor value\n");
>> +				/* don't update the trickle charger regs */
>> +				val = val_old;
>> +			}
>> +		}
>>   
>> -		if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
>> +		/* only update EEPROM if changes are necessary */
>> +		if (val_old != val) {
>>   			ret = rv3028_update_cfg(rv3028, RV3028_BACKUP, RV3028_BACKUP_TCE |
>> -						 RV3028_BACKUP_TCR_MASK, RV3028_BACKUP_TCE | i);
>> +						RV3028_BACKUP_TCR_MASK, val);
>>   			if (ret)
>>   				return ret;
>> -		} else {
>> -			dev_warn(&client->dev, "invalid trickle resistor value\n");
>>   		}
>>   	}
>>   
>> -- 
>> 2.25.1
>>
>