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USB: EHCI: fix command register configuration lost problem

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The 3d9545cc375d117554a9b35dfddadf9189c62775(EHCI: maintain the
ehci->command value properly) introducs one command register
configuration lost problem by the below line in ehci_reset:

	ehci->command = ehci_readl(ehci, &ehci->regs->command);

After writting RESET into command register, it is restored to
its default value per EHCI spec[1], so the previous configuration
will be lost, and may introduce some problems reported recently:
	- imx51 Babbage board detect usb hub failed[2], reported
	by Richard Zhao.
	- mouse and keyboard hangs in linux-next found by
	Dan Carpenter and Greg-KH.

So this patch just removes the line to fix these problems, and
keep configurating command register consistent as before the commit
3d9545cc(EHCI: maintain the ehci->command value properly).

[1], 4.1 Host Controller Initialization of EHCI Specification 1.0
[2], failed dmesg log:
	usb 1-1: new high-speed USB device number 2 using mxc-ehci
	hub 1-1:1.0: USB hub found
	hub 1-1:1.0: 7 ports detected
	mxc-ehci mxc-ehci.1: fatal error
	mxc-ehci mxc-ehci.1: HC died; cleaning up
	mxc-ehci mxc-ehci.1: force halt; handshake f5780344 00004000 00004000 -> -110
	mxc-ehci mxc-ehci.1: HC died; cleaning up
	usb 1-1: USB disconnect, device number 2

Reported-by: Richard Zhao <richard.zhao@freescale.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Chen Peter-B29397 <B29397@freescale.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei 2012-05-19 23:11:19 +08:00 committed by Greg Kroah-Hartman
parent 4e09dcf20f
commit 1c01f1d9a6
1 changed files with 0 additions and 1 deletions
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1
drivers/usb/host/ehci-hcd.c
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@ -352,7 +352,6 @@ static int ehci_reset (struct ehci_hcd *ehci)
if (ehci->debug)
dbgp_external_startup();
ehci->command = ehci_readl(ehci, &ehci->regs->command);
ehci->port_c_suspend = ehci->suspended_ports =
ehci->resuming_ports = 0;
return retval;