usb: host: ehci-msm: Fix register initialization

The default value for the 'transceiver select' field of
the PORTSC register may not always be correct. Previously
the phy-msm-usb driver would do this for us, but since
ehci-msm can now be instantiated standalone without any PHY
driver, the register needs to be explicitly initialized to
ULPI mode to properly communicate with the PHY.

This is not readily apparent, as firmware or bootloader code
also happen to pre-initialize this for us. However, it can
manifest when performing a driver unbind/rebind as follows:

 cd /sys/bus/platform/drivers/msm_hsusb_host
 echo QCOM8040:00 > unbind
 echo QCOM8040:00 > bind

The EHCI core executes a controller reset as part of this,
and as a result the register in question would revert to
its default state and must be re-initialized properly.
Furthermore this may be useful in the future when adding
PM suspend/resume support.
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-msm.c

@@ -56,6 +56,8 @@ static int ehci_msm_reset(struct usb_hcd *hcd)
 	if (retval)
 		return retval;
 
+	/* select ULPI phy and clear other status/control bits in PORTSC */
+	writel(PORTSC_PTS_ULPI, USB_PORTSC);
 	/* bursts of unspecified length. */
 	writel(0, USB_AHBBURST);
 	/* Use the AHB transactor, allow posted data writes */