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

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Message-ID: <20210811195327.GA966160@roeck-us.net>
Date:   Wed, 11 Aug 2021 12:53:27 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: (pmbus/bpa-rs600) Add workaround for
 incorrect Pin max

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.

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.

Guenter

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