From: Alan Stern <stern@rowland.harvard.edu>
To: John Donnelly <john.p.donnelly@oracle.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: ehci-pci : WARNING: CPU: 0 PID: 347 at kernel/dma/direct.c:34
Date: Tue, 31 Mar 2020 14:21:11 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.2003311413040.17645-100000@netrider.rowland.org> (raw)
In-Reply-To: <86E5B81F-DD9D-42E8-A687-D4593FA734AE@oracle.com>
On Tue, 31 Mar 2020, John Donnelly wrote:
> Hi ,
>
> One more follow up question.
>
> How does a X86 kernel know where to look for USB buses/control
> registers ? I am aware PowerPC has a device-tree that is passed by
> reference from UBoot that contains known devices.
Some of the information comes from ACPI tables in the BIOS. Other
parts of it come from the components on the motherboard (for example,
devices attached to a PCI bus can be discovered directly by the
system).
> For the BCM device :
>
> Bus 03.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
>
> Is there a corresponding register set I can examine ?
Yes. For example, you can look at the files under
/sys/kernel/debug/usb/uhci/. You can also use lspci and other related
PCI utilities.
Alan Stern
next prev parent reply other threads:[~2020-03-31 18:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-28 4:11 ehci-pci : WARNING: CPU: 0 PID: 347 at kernel/dma/direct.c:34 John Donnelly
2020-03-28 7:08 ` Greg KH
2020-03-28 15:34 ` Alan Stern
2020-03-28 15:37 ` Alan Stern
2020-03-28 18:05 ` John Donnelly
2020-03-30 18:36 ` John Donnelly
2020-03-30 19:41 ` Alan Stern
2020-03-30 20:11 ` John Donnelly
2020-03-31 2:10 ` John Donnelly
2020-03-31 14:17 ` Alan Stern
2020-03-31 16:07 ` John Donnelly
2020-03-31 17:43 ` John Donnelly
2020-03-31 18:21 ` Alan Stern [this message]
2020-04-07 13:49 ` John Donnelly
2020-04-07 13:53 ` Alan Stern
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