On Tue, May 09, 2017 at 12:51:53PM +0530, Jayan John wrote: > On Tue, May 9, 2017 at 6:24 AM, Peter Chen <hzpeterchen@xxxxxxxxx> wrote: > > On Fri, May 05, 2017 at 10:40:01AM +0530, Jayan John wrote: > >> I would like to add CDP (charging downstream port) capability over my > >> OTG port in host mode. I am using an iMX6q platform with Chipidea HDRC > >> (highspeed dual role controller) with 4.1 kernel. > >> > >> Looked at a bunch of documents like USB Battery Charging Specification > >> and USB Power Delivery specification, it is clear that there is a > >> handshake over D+ and D- before enumeration to identify whether a host > >> supports CDP or not. It occurs in two steps. A primary handshake to > >> detect SDP vs CDP/ DCP where host will respond with D- voltage greater > >> than 0.3 V and less than 0.8 V. A secondary handshake to detect CDP vs > >> DCP where DCP will be indicated witha response of D+ voltage greater > >> than 0.3 V and less than 0.8 V. > >> > >> I believe the handshake can only be supported by using a CDP emulator > >> or a USB charging port controller. But I would like to investigate the > >> possibility of achieving this handshake with only driver changes in > >> PHY or controller i.e. without any additional hardware chips or > >> circuitry. > >> > >> Does anyone have any viewpoints on whether CDP charging can be > >> achieved without any additional hardware changes over Chipidea HDRC in > >> host mode? > >> > > > > The imx6 series USB PHY supports USB charger detection, and the internal > > tree implements it at: drivers/usb/chipidea/usbmisc_imx.c if you are > > using v4.1 release. Due to there is no USB charger framework at > > mainline, this part of code has still not upstream. > > > > -- > > > > Best Regards, > > Peter Chen > > Thank you Peter. > > I think you may have misunderstood my question. The imx6 USB charger > detection block I believe is used by a upstream facing device to > detect what type of down-stream facing charger it is connected to. > > My requirement is kind of the opposite.. here the imx6 will be used as > the down-stream facing charger i.e. attempt to support cdp charging > (instead of sdp) after role reveral with imx6 otg in host mode. > > I know this is feasible with additional hardware such as a CDP > emulator or a USB charging port controller. I was hoping you might > have an insight on whether this is possible without any additional > hardware i.e. only with changes in USB PHY / controller. > No, the PHY doesn't support host charger function. -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
