linux-kernel - Re: [v6,3/4] pmbus (core): Add virtual page config bit

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Date:   Wed, 29 Nov 2017 13:15:18 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Jeffery <andrew@...id.au>
Cc:     linux-hwmon@...r.kernel.org, jdelvare@...e.com, corbet@....net,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, joel@....id.au, openbmc@...ts.ozlabs.org
Subject: Re: [v6,3/4] pmbus (core): Add virtual page config bit

On Mon, Nov 20, 2017 at 03:12:05PM +1030, Andrew Jeffery wrote:
> Some circumstances call for virtual pages, to expose multiple values
> packed into an extended PMBus register in a manner non-compliant with
> the PMBus standard. An example of this is the Maxim MAX31785 controller,
> which extends the READ_FAN_SPEED_1 PMBus register from two to four bytes
> to support tach readings for both rotors of a dual rotor fan. This extended
> register contains two word-sized values, one reporting the rate of the
> fastest rotor, the other the rate of the slowest. The concept of virtual
> pages aids this situation by mapping the page number onto the value to be
> selected from the vectored result.
> 
> We should not try to set virtual pages on the device as such a page
> explicitly doesn't exist; add a flag so we can avoid doing so.
> 
> Signed-off-by: Andrew Jeffery <andrew@...id.au>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/pmbus/pmbus.h      |  2 ++
>  drivers/hwmon/pmbus/pmbus_core.c | 27 ++++++++++++++++++---------
>  2 files changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index b54d7604d3ef..d39d506aa63e 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -372,6 +372,8 @@ enum pmbus_sensor_classes {
>  #define PMBUS_HAVE_PWM12	BIT(20)
>  #define PMBUS_HAVE_PWM34	BIT(21)
>  
> +#define PMBUS_PAGE_VIRTUAL	BIT(31)
> +
>  enum pmbus_data_format { linear = 0, direct, vid };
>  enum vrm_version { vr11 = 0, vr12, vr13 };
>  
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index edc25efe7552..e215bbd403a5 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -161,18 +161,27 @@ EXPORT_SYMBOL_GPL(pmbus_clear_cache);
>  int pmbus_set_page(struct i2c_client *client, int page)
>  {
>  	struct pmbus_data *data = i2c_get_clientdata(client);
> -	int rv = 0;
> -	int newpage;
> +	int rv;
> +
> +	if (page < 0 || page == data->currpage)
> +		return 0;
>  
> -	if (page >= 0 && page != data->currpage) {
> +	if (!(data->info->func[page] & PMBUS_PAGE_VIRTUAL)) {
>  		rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
> -		newpage = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
> -		if (newpage != page)
> -			rv = -EIO;
> -		else
> -			data->currpage = page;
> +		if (rv < 0)
> +			return rv;
> +
> +		rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
> +		if (rv < 0)
> +			return rv;
> +
> +		if (rv != page)
> +			return -EIO;
>  	}
> -	return rv;
> +
> +	data->currpage = page;
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(pmbus_set_page);
>