linux-kernel - Re: [PATCH v2 2/3] hwmon (xdpe12284): Add support for xdpe11280

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Date:   Sat, 26 Feb 2022 16:32:37 +0100
From:   Marcello Sylvester Bauer <sylv@...v.io>
To:     Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 2/3] hwmon (xdpe12284): Add support for xdpe11280

On Fri, 2022-02-25 at 08:39 -0800, Guenter Roeck wrote:
> On 2/21/22 04:13, sylv wrote:
> > On Thu, 2022-02-17 at 11:25 -0800, Guenter Roeck wrote:
> > > On 2/17/22 10:38, sylv wrote:
> > > [ ... ]
> > > 
> > > > > 
> > > > > That makes me wonder if the chip needs to be added to this
> > > > > driver
> > > > > in
> > > > > the first
> > > > > place, or if it could be added to pmbus.c instead. Any idea ?
> > > > 
> > > > Oh, we did wrote a standalone driver too, and it works fine.
> > > > Maybe it's better to upsteam it instead. :)
> > > 
> > > No, I meant if it would make sense to just add something like
> > > 
> > >          {"xdpe11280", (kernel_ulong_t)&pmbus_info_one },
> > > 
> > > to drivers/hwmon/pmbus/pmbus.c.
> > > 
> > > You only really need a standalone driver if it does something
> > > special, such as a workaround for some register access (like
> > > the xdpe12284 driver), or if support for manufacturer specific
> > > registers is desired or needed. That would, for example, be
> > > useful
> > > if the xdpe11280 supports per-phase sensors.
> > > 
> > > Thanks,
> > > Guenter
> > 
> > Hi,
> > 
> > I tested if the xdpe11280 can use the generic pmbus driver.
> > Everything
> > works fine except it does only detect READ_TEMPERATURE_1 on page 0.
> > Looking at the pmbus_find_sensor_groups function it looks like only
> > some commands are probed on each page (READ_VOUT, READ_IOUT, and
> > READ_POUT) but not READ_TEMPERATURE_1.
> > The PMBus spec 1.3.1 tells us: "Each page may offer the full range
> > of
> > PMBus commands available for each output or non-PMBus device." How
> > could we adapt the generic driver so that it is possible to probe
> > commands for each page?
> > 
> 
> The problem is the "may". Some chips don't implement multi-page
> support especially for temperature sensors. So we'll have to go
> with adding support to the existing driver.
> 
> Guenter

sgtm. So I'll continue working on this patch set.

> 
> > Furthermore, It would be great to add regulator and DT support. I
> > created a WIP branch on GitHub with a possible way to implement
> > this:
> > https://github.com/9elements/linux/tree/upstreaming_pmbus_regulator_wip
> > 
> > What do you think?
> > 
> > Thanks,
> > Marcello
> > 
>