RE: [PATCH 4.16 REGRESSION fix] Revert "typec: tcpm: Only request matching pdos"

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Hi,
> -----Original Message-----
> From: linux-usb-owner@xxxxxxxxxxxxxxx
> [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Heikki Krogerus
> Sent: 2018年3月6日 20:33
> To: Hans de Goede <hdegoede@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Guenter Roeck
> <linux@xxxxxxxxxxxx>; linux-usb@xxxxxxxxxxxxxxx; Badhri Jagan Sridharan
> <badhri@xxxxxxxxxx>
> Subject: Re: [PATCH 4.16 REGRESSION fix] Revert "typec: tcpm: Only request
> matching pdos"
> 
> On Tue, Mar 06, 2018 at 10:50:05AM +0100, Hans de Goede wrote:
> > Commit 57e6f0d7b804 ("typec: tcpm: Only request matching pdos") is
> > causing a regression, before this commit e.g. the GPD win and GPD
> > pocket devices were charging at 9V 3A with a PD charger, now they are
> > instead slowly discharging  at 5V 0.4A, as this commit causes the
> > ports max_snk_mv/ma/mw settings to be completely ignored.
> >

So max_snk_mv/ma/mw settings are back, I am dealing with PD properties
definition, so want to ask for long term, should we keep them, or use the
reverting patch way(only compare sink PDOs Vs source PDOs) but fix the
problem with it.

Thanks
Jun Li

> > Arguably the way to fix this would be to add a PDO_VAR() describing
> > the voltage range to the snk_caps of boards which can handle any
> > voltage in their range, but the "typec: tcpm: Only request matching
> > pdos" commit looks at the type of PDO advertised by the source/charger
> > and if that is fixed (as it typically is) only compairs against
> > PDO_FIXED entries in the snk_caps so supporting a range of voltage
> > would require adding a PDO_FIXED entry for *every possible* voltage to
> snk_caps.
> >
> > AFAICT there is no reason why a fixed source_cap cannot be matched
> > against a variable snk_cap, so at a minimum the commit should be
> > rewritten to support that.
> >
> > For now lets revert the "typec: tcpm: Only request matching pdos"
> > commit, fixing the regression.
> >
> > Cc: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> 
> You are correct. The patch should be rewritten.
> 
> Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> 
> 
> Thanks,
> 
> --
> heikki
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