linux-kernel - Re: [PATCH v2 08/14] power: supply: Add power_supply_set_input_current_limit_from

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Message-ID: <20170816192132.GV3930@atomide.com>
Date:   Wed, 16 Aug 2017 12:21:33 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sebastian Reichel <sre@...nel.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Liam Breck <liam@...workimprov.net>, linux-i2c@...r.kernel.org,
        linux-pm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org
Subject: Re: [PATCH v2 08/14] power: supply: Add
 power_supply_set_input_current_limit_from_supplier helper

* Hans de Goede <hdegoede@...hat.com> [170816 10:38]:
> Hi,
> 
> On 16-08-17 17:54, Tony Lindgren wrote:
> > * Hans de Goede <hdegoede@...hat.com> [170815 13:06]:
> > > On some devices the USB Type-C port power (USB PD 2.0) negotiation is
> > > done by a separate port-controller IC, while the current limit is
> > > controlled through another (charger) IC.
> > > 
> > > It has been decided to model this by modelling the external Type-C
> > > power brick (adapter/charger) as a power-supply class device which
> > > supplies the charger-IC, with its voltage-now and current-max representing
> > > the negotiated voltage and max current draw.
> > > 
> > > This commit adds a power_supply_set_input_current_limit_from_supplier
> > > helper function which charger power-supply drivers can call to get
> > > the max-current from their supplier and have this applied
> > > through their set_property call-back to their input-current-limit.
> > 
> > Hmm so can this also be used for the USB gadget subsystem
> > to tell charge controller when it's OK to enable 500mA
> > charging after enumeration?
> 
> I'm not sure that that would be best modeled this way. Perhaps
> the phy-driver can directly control the gpio you have for that,
> that seems better then trying to solve this with cross subsystem
> calls which are always tricky.

I don't think the phy driver knows either when the system
has enumerated as a gadget..

> > FYI, that's controlled by the bq24190 pin named OTG that should
> > be only set high after enumeration. Any ideas how that is wired
> > on your device? Does it connect to the USB PHY or to a GPIO
> > line?
> 
> I believe it is just hardwired to be logical high all the time
> on my board.

OK thanks for checking.

Tony