linux-kernel - Re: [PATCH 2/2] usb: typec: ucsi: Don't create power supplies for dGPUs

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Message-ID: <2023051742-guiding-footing-3527@gregkh>
Date:   Wed, 17 May 2023 20:58:49 +0200
From:   Greg KH <greg@...ah.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Mario Limonciello <mario.limonciello@....com>,
        heikki.krogerus@...ux.intel.com, rafael@...nel.org,
        ajayg@...dia.com, linux-i2c@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, Evan.Quan@....com, Lijo.Lazar@....com,
        Sanket.Goswami@....com
Subject: Re: [PATCH 2/2] usb: typec: ucsi: Don't create power supplies for
 dGPUs

On Wed, May 17, 2023 at 08:14:13PM +0300, Andy Shevchenko wrote:
> On Tue, May 16, 2023 at 01:25:41PM -0500, Mario Limonciello wrote:
> > power_supply_is_system_supplied() checks whether any power
> > supplies are present that aren't batteries to decide whether
> > the system is running on DC or AC.  Downstream drivers use
> > this to make performance decisions.
> > 
> > Navi dGPUs include an UCSI function that has been exported
> > since commit 17631e8ca2d3 ("i2c: designware: Add driver
> > support for AMD NAVI GPU").
> > 
> > This UCSI function registers a power supply since commit
> > 992a60ed0d5e ("usb: typec: ucsi: register with power_supply class")
> > but this is not a system power supply.
> > 
> > As the power supply for a dGPU is only for powering devices connected
> > to dGPU, create a device property to indicate that the UCSI endpoint
> > is only for the scope of `POWER_SUPPLY_SCOPE_DEVICE`.
> 
> ...
> 
> > +static const struct property_entry dgpu_properties[] = {
> > +	/* USB-C doesn't power the system */
> > +	PROPERTY_ENTRY_U8("scope", POWER_SUPPLY_SCOPE_DEVICE),
> > +	{},
> 
> Comma is not needed in terminator entry.

But it's encouraged!