[g1-hackers] USB Host mode on G1

[Jay Freeman (saurik)]

As Mike said, this line of thought (just trying to activate things) won't help. This feature is something the underlying USB driver needs to support, and the one for the Qualcomm MSM chipset (what I believe is an accurate description of where the USB functionality is) that is in Android does not support this.

The driver can be found in the kernel under:

./include/asm-arm/arch-msm/msm_hsusb.h
./drivers/usb/function/msm_hsusb.c
./drivers/usb/function/msm_hsusb_hw.h

This is certainly not enough information to actually implement host mode, but the _hw.h file does have a bit breakdown for at least most of the registers.

The most specific register in question, the one that chooses what mode it is in, is this one:

     46 #define USB_USBMODE          (MSM_USB_BASE + 0x01A8)

     59 #define USBMODE_DEVICE 2
     60 #define USBMODE_HOST   3

The code that actually selects device mode (which doesn't bother using the flags... grr) is here:

   1047         /* select DEVICE mode */
   1048         writel(0x12, USB_USBMODE);
   1049         msleep(1);

I am not even certain, though, what the 0x10 part is, much less what other changes would have to be done to the driver (which may be many) to actually activate host mode correctly. Someone much more familiar with USB devices, however, may recognize standard names or standard organizations on this chip and be able to figure it out, though (I know next to nothing about USB).

Sincerely,
Jay Freeman (saurik)
http://www.saurik.com/

  ----- Original Message ----- 
  From: Frank Murray 
  To: Hacking the Android T-Mobile G1 
  Sent: Thursday, January 01, 2009 4:12 AM
  Subject: Re: [g1-hackers] USB Host mode on G1


  Is there any information available on the chipset used and it's register set? I've built in support for a number of host mode drivers but it's a guessing game whether the hardware is based on Uhci/ohci/ehci or a custom solution. Host mode on the Neo can be activated by writing to the OHCI part of /sys so I was hoping that the G1 had a similar facility.



    On Dec 31, 2008 6:25 PM, "Mike Lockwood" <lockwood at android.com> wrote:

    Short answer: No

    Long answer:  The chipset supports OTG so it is theoretically
    possible, but I'm not sure if the G1 hardware would need to be
    modified.  Also, we have no OTG support in the USB driver, and none of
    the higher level code in android supports host side USB.

    Mike

    On Wed, Dec 31, 2008 at 1:03 PM, Mike Down <nikropht at gmail.com> wrote: > Has anyone been able to ge...

    --
    Mike Lockwood
    Google android team

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