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Subject: Re: [PATCH] hwmon: (pmbus) Add support for 2nd Gen Renesas digital
 multiphase
To:     Grant Peltier <grantpeltier93@gmail.com>
Cc:     linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org,
        openbmc@lists.ozlabs.org, adam.vaughn.xh@renesas.com,
        zaitsev@google.com
References: <20200228212349.GA1929@raspberrypi>
 <20200228225848.GA14676@roeck-us.net> <20200228235206.GA3468@raspberrypi>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <1a456016-682a-2d53-767b-fe09784883ef@roeck-us.net>
Date:   Fri, 28 Feb 2020 17:55:44 -0800
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On 2/28/20 3:52 PM, Grant Peltier wrote:
> Hi Guenter,
> 
> Thank you for your expedient review. I will need to consult with my
> coworkers to determine a more appropriate driver name. In the meantime I
> will make the desired changes and I will also create a document for the
> driver, which I will submit as a linked but separate patch.
> 
> With regard to the part numbers, this family of parts is currently in
> the process of being released and we have not yet published all of the
> corresponding datasheets. However, I have been assured that all of the
> parts listed are slated to have a datasheet published publicly in the near
> future.
> 
That would be great.

As for the driver name, I had a look into drivers/hwmon/pmbus/isl68137.c,
and I don't immediately see why the new chips would warrant a new driver.
The only differences seem to be that VMON is a new command, and of course
only the ISL68137 supports AVL. But then there is, for example, ISL68127,
which is again quite similar. The only other difference as far as I can
see is input voltage scaling, but that doesn't warrant a separate driver
(and, of course, I have no means to validate if input voltage scaling
is indeed different for all the new chips).

Overall I would suggest to extend the isl68137 driver. I would also
suggest to not add separate tables for each of the rail configurations
but use the three-phase entry as starting point, copy it, and adjust its
values as needed.

For the multi-phase chips, I question if reporting the input voltage
for each phase make sense. Is it really a different voltage ? For IIN
and PIN, the question is if the registers are indeed paged, since they
are not paged in the older chips.

Guenter