[PATCH v6 23/25] usb: chipidea: Pullup D+ in device mode via phy APIs

[Stephen Boyd]

Quoting Peter Chen (2017-01-12 19:35:36)
> On Thu, Jan 12, 2017 at 02:49:51PM -0800, Stephen Boyd wrote:
> > 
> > With the boards I have, vbus is not routed to the phy. Instead, there's
> > a vbus comparator on the PMIC where the vbus line from the usb
> > receptacle is sent. The vbus extcon driver probes the comparator on the
> > PMIC to see if vbus is present or not and then notifies extcon users
> > when vbus changes.
> > 
> > The ULPI register we write in the phy is a vendor specific register
> > (called MISC_A) that has two bits. If you look at
> > qcom_usb_hs_phy_set_mode() in this series you'll see that we set
> > VBUSVLDEXTSEL and VBUSVLDEXT. VBUSVLDEXTSEL controls a mux in the phy
> > that chooses between an internal comparator, in the case where vbus goes
> > to the phy, or an external signal input to the phy, VBUSVLDEXT, to
> > consider as the "session valid" signal. It looks like the session valid
> > signal drives the D+ pullup resistor in the phy. These bits in MISC_A
> > don't matter when the phy is in host mode.
> > 
> > So when the board doesn't route vbus to the phy, we have to toggle the
> > VBUSVLDEXT bit to signal to the phy that the vbus is there or not. I
> > also see that we're not supposed to toggle the VBUSVLDEXTSEL bit when in
> > "normal" operating mode. So perhaps we should do everything in the
> > qcom_usb_hs_phy_set_mode() routine during the role switch as you
> > suggest, except toggle the VBUSVLDEXT bit. Toggling the VBUSVLDEXT bit
> > can be done via some new phy op when the extcon triggers?
> 
> Why not call phy_set_mode(phy, DEVICE) directly at ci_handle_vbus_change when
> you get extcon vbus event?
> 

Right, I can call phy_set_mode(phy, DEVICE) there, but is that correct?
How do we signal vbus is gone, with phy_set_mode(phy, HOST)? Mode
doesn't seem the same as "vbus status changed" so this feels wrong.