tree 9f2599156b1075a0b9e7728a2402dff9b3e3b326
parent 7bbbb3c6d861e24149a68e9b89d7f89aa7d3cf2f
author Marek Vasut <marex@denx.de> 1438737562 +0200
committer Marek Vasut <marex@denx.de> 1438788163 +0200

usb: Fix device detection code

The code in question polls an USB port status via USB_REQ_GET_STATUS
to determine whether there is a device on the port or not. The way to
figure that out is to check two bits. Those are wPortChange[0] and
wPortStatus[0].

The wPortChange[0] indicates whether some kind of a connection status
change happened on a port (a device was plugged or unplugged). The
wPortStatus[0] bit indicates the status of the connection (plugged or
unplugged).

The current code tests whether wPortChange[0] == wPortStatus[0] and
if that's the case, considers the loop polling for the presence of a
USB device on port finished.

This works for most USB sticks, since they come up really quickly and
trigger the USB port change detection before the first iteration of the
detection loop happens. Thus, both wPortChange[0] and wPortStatus[0]
are set to 1 and thus equal. The loop is existed in it's first iteration
and the stick is detected correctly.

The problem is with some obscure USB sticks, which take some time before
they pop up on the bus after the port was enabled. In this case, both
the wPortChange[0] and wPortStatus[0] are 0. They are equal again, so
the loop again exits in the first iteration, but this is incorrect, as
such USB stick didn't have the opportunity to get detected on the bus.

Rework the code such, that it checks for wPortChange[0] first to test
if any connection change happened at all. If no change occured, keep
polling. If a change did occur, test the wPortStatus[0] to see there is
some device present on the port and only if this is the case, break out
of the polling loop.

This patch also trims down the duration of the polling loop from 10s
per port to 1s per port. This is still annoyingly long, but there is
no better option in case of U-Boot unfortunatelly. This change will
most likely increase the duration of 'usb start' on some platforms,
but this is needed to fix a bug.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Hans de Goede <hdegoede@redhat.com>