On Tue, May 9, 2017 at 1:10 PM, Peter Chen <hzpeterchen@xxxxxxxxx> wrote: > 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. > Thank you for confirming that Peter. I needed that information. I will keep this topic open for another day or two just in case there are any other related comments from the others. Best regards, Jayan -- 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
