On 11/01/2013 07:55 PM, Alan Stern wrote:
On Fri, 1 Nov 2013, Valentine wrote:
The USB HDC PCI deferred probing could be used on R-Car. But I'm not sure how to make a particular
PCI USB HDC device attached to a particular PCI host controller on a particular SoC defer its probing
while waiting for the USB phy. At the same time other identical PCI USB HCD devices (with the same PCI id)
on the same SoC should be probed as usual.
That is the hard part. That's what we need to discuss.
And not just on the linux-usb mailing list. Get other people
(especially PCI people) involved too.
We can't use PCI ids here to distinguish between PCI USB HCD devices. Neither can we use PCI busses
to distinguish between PCI host controllers, since bus numbers are assigned dynamically.
There must be some way for you to tell which PCI devices use the PHY.
But I'm not a PCI expert, and I'm not familiar with your platform.
It looks that it's quite hard to do that without bigger hacks in the PCI USB HCD driver that are
most likely not to be used on any other platforms except for R-Car.
You never know what will happen in the future. Besides, even if nobody
else needs to do this for a PCI device, you can be certain that the
same sort of thing will be needed for devices on other buses. A
suitably general solution would help them too.
Alan Stern
OK, I've tried to come up with more or less universal solution to defer HCD probing
until the external USB phy is ready. I'll start a new thread with the RFC patches in a bit.
Thanks,
Val.
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