linux-kernel - Re: [PATCH v2 2/2] hwmon: pmbus: add driver for ltp8800-1a, ltp8800-4a, and ltp8800-2

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Message-ID: <c6b1718a-1a16-4670-b9b6-d8d9bebad4f0@roeck-us.net>
Date: Fri, 8 Nov 2024 06:31:12 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: "Encarnacion, Cedric justine" <Cedricjustine.Encarnacion@...log.com>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
 "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
 "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>
Cc: Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
 Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Peter Yin <peteryin.openbmc@...il.com>,
 Noah Wang <noahwang.wang@...look.com>, Marek Vasut <marex@...x.de>,
 Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2 2/2] hwmon: pmbus: add driver for ltp8800-1a,
 ltp8800-4a, and ltp8800-2

On 11/7/24 23:44, Encarnacion, Cedric justine wrote:
>> -----Original Message-----
>> From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
>> Sent: Thursday, November 7, 2024 9:45 AM
>> To: Encarnacion, Cedric justine <Cedricjustine.Encarnacion@...log.com>;
>> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
>> i2c@...r.kernel.org; linux-doc@...r.kernel.org; linux-
>> hwmon@...r.kernel.org
>> Cc: Jean Delvare <jdelvare@...e.com>; Jonathan Corbet <corbet@....net>;
>> Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>; Rob Herring
>> <robh@...nel.org>; Krzysztof Kozlowski <krzk+dt@...nel.org>; Conor Dooley
>> <conor+dt@...nel.org>; Peter Yin <peteryin.openbmc@...il.com>; Noah
>> Wang <noahwang.wang@...look.com>; Marek Vasut <marex@...x.de>;
>> Lukas Wunner <lukas@...ner.de>
>> Subject: Re: [PATCH v2 2/2] hwmon: pmbus: add driver for ltp8800-1a,
>> ltp8800-4a, and ltp8800-2
>>
>> [External]
>>
>> On 11/5/24 19:09, Cedric Encarnacion wrote:
>>> LTP8800-1A 54V, 150A DC/DC µModule Regulator with PMBus Interface
>>> LTP8800-4A 54V, 200A DC/DC µModule Regulator with PMBus Interface
>>> LTP8800-2 54V, 135A DC/DC μModule Regulator with PMBus Interface
>>>
>>> The LTP8800 is a family of step-down μModule regulators that provides
>>> microprocessor core voltage from 54V power distribution architecture. It
>>> features telemetry monitoring of input/output voltage, input current,
>>> output power, and temperature over PMBus.
>>>
>>> Signed-off-by: Cedric Encarnacion <cedricjustine.encarnacion@...log.com>
>>
>> Looking closer into the datasheets, I found that the PMBus commands are
>> identical
>> to those of ADP1055, and an extension of the ADP1050 driver to support
>> ADP1055
>> has been submitted.
>>
>> With this in mind, please explain why this series warrants a new driver instead
>> of just extending the existing driver to support LTP8800.
> 
> It also appears that the LTP8800-1A regulator makes use of
> factory-programmed ADP1055 but this is not explicitly stated for other
> variants. Initially, I thought a new client driver would be reasonable
> since this device is intended as a regulator while ADP1050/ADP1055 is a
> more customizable digital controller, and both have their own multiple

We use the same driver for many variants of ltc2978. We should do the same here.

> variants. Indeed, it may be more reasonable to extend existing driver since
> they are exposing the same feature. In this case, can this be done in
> succeeding version/s of this series?
> 

Succeeding version, but please synchronize with the engineer adding support
for adp1055 to the adp1050 driver. Another option would be to make adding support
for adp1051/adp1055 and adding support for ltp880X chips a patch series. The
introductory patch could then reference the original patch series.

Thanks,
Guenter