linux-kernel - Re: [PATCH 2/2] hwmon: (pmbus/bpa-rs600) Add workaround for incorrect Pin max

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Date:   Wed, 11 Aug 2021 23:25:58 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     "jdelvare@...e.com" <jdelvare@...e.com>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] hwmon: (pmbus/bpa-rs600) Add workaround for incorrect
 Pin max


On 12/08/21 11:18 am, Guenter Roeck wrote:
> On Wed, Aug 11, 2021 at 10:19:44PM +0000, Chris Packham wrote:
>> On 12/08/21 7:53 am, Guenter Roeck wrote:
>>> On Wed, Aug 11, 2021 at 04:17:38PM +1200, Chris Packham wrote:
>>>> BPD-RS600 modules running firmware v5.70 misreport the MFR_PIN_MAX.
>>>> The indicate a maximum of 1640W instead of 700W. Detect the invalid
>>>> reading and return a sensible value instead.
>>>>
>>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>>> ---
>>>>    drivers/hwmon/pmbus/bpa-rs600.c | 21 ++++++++++++++++++++-
>>>>    1 file changed, 20 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/hwmon/pmbus/bpa-rs600.c b/drivers/hwmon/pmbus/bpa-rs600.c
>>>> index d495faa89799..f4baed9ce8a4 100644
>>>> --- a/drivers/hwmon/pmbus/bpa-rs600.c
>>>> +++ b/drivers/hwmon/pmbus/bpa-rs600.c
>>>> @@ -65,6 +65,24 @@ static int bpa_rs600_read_vin(struct i2c_client *client)
>>>>    	return ret;
>>>>    }
>>>>    
>>>> +/*
>>>> + * The firmware on some BPD-RS600 models incorrectly reports 1640W
>>>> + * for MFR_PIN_MAX. Deal with this by returning a sensible value.
>>>> + */
>>>> +static int bpa_rs600_read_pin_max(struct i2c_client *client)
>>>> +{
>>>> +	int ret;
>>>> +
>>>> +	ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_PIN_MAX);
>>>> +	if (ret < 0)
>>>> +		return ret;
>>>> +
>>>> +	if (ret == 0x0b34)
>>>> +		return 0x095e;
>>> The comments from the descriotion need to be here.
>> will update
>>> Thanks,
>>> Guenter
>>>
>>>> +
>>>> +	return ret;
>>>> +}
>>>> +
>>>>    static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int phase, int reg)
>>>>    {
>>>>    	int ret;
>>>> @@ -92,7 +110,8 @@ static int bpa_rs600_read_word_data(struct i2c_client *client, int page, int pha
>>>>    		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_IOUT_MAX);
>>>>    		break;
>>>>    	case PMBUS_PIN_OP_WARN_LIMIT:
>>>> -		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_PIN_MAX);
>>>> +	case PMBUS_MFR_PIN_MAX:
>>>> +		ret = bpa_rs600_read_pin_max(client);
>>> So the idea is to return the same value for PMBUS_PIN_OP_WARN_LIMIT
>>> (max_alarm) and PMBUS_MFR_PIN_MAX (rated_max) ? That doesn't really
>>> make sense. The meaning of those limits is distinctly different.
>> For the BPA-RS600/BPD-RS600 these appear to be treated the same.
> What a mess.
*sigh* I know. I've also got another 2 BluTek supplies I haven't got 
round to dealing with yet.
> This needs to be documented in the driver, including the
> behavior if any of those attributes is written into.

Mercifully these attributes are all read-only. So at least we don't have 
to deal with that.

It's probably not too late to return -ENXIO for the WARN_LIMITs and have 
lm-sensors display the rated_max (we also have a custom consumer of the 
sysfs API that I'd need to sort out).

>
> Guenter
>
>>> Guenter
>>>
>>>>    		break;
>>>>    	case PMBUS_POUT_OP_WARN_LIMIT:
>>>>    		ret = pmbus_read_word_data(client, 0, 0xff, PMBUS_MFR_POUT_MAX);
>>>> -- 
>>>> 2.32.0
>>>>