Re: Re [patch 2/3] fastboot: turn the USB hostcontroller initcallsinto async initcalls
From: Alan Stern
Date: Sat Jul 19 2008 - 16:34:21 EST
On Sat, 19 Jul 2008, Arjan van de Ven wrote:
> On Sat, 19 Jul 2008 11:25:29 -0400 (EDT)
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On 18 July, 2008, Arjan van de Ven wrote:
> > > From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
> > > Subject: [PATCH] fastboot: turn the USB hostcontroller initcalls
> > > into async initcalls
> > >
> > > the USB host controller init calls take a long time, mostly due to a
> > > "minimally 100 msec" delay *per port* during initialization.
> > > These are prime candidates for going in parallel to everything else.
> > >
> > > The USB device ordering is not affected by this due to the
> > > serialized-within-eachother property of async initcalls.
> > Where is this "minimally 100 msec" per-port delay you refer to?
> > Offhand I can't recall any such delays in the init routines.
> it's here (in drivers/usb/core/hub.c::hub_power_on):
> "non-switchable hub\n");
> for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++)
> set_port_feature(hub->hdev, port1, USB_PORT_FEAT_POWER);
> /* Wait at least 100 msec for power to become stable */
> msleep(max(pgood_delay, (unsigned) 100));
> at least my eeepc901 hits that like 6 or 7 times
> (because if I shorten the 100 the boot goes a ton faster.. but that's
> obviously just a bad hack)
That isn't a *per-port* delay. It's a single delay used concurrently
for all the ports in the root hub; the msleep call occurs outside the
Maybe you meant 100 ms *per controller*. I agree, it's best for these
delays to occur in parallel. Now if only we could do the same with
suspend and resume...
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/