Re: BUG: one patch causes imx51 Babbage board detect usb hub failed

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On Thu, May 17, 2012 at 7:41 PM, Richard Zhao
<richard.zhao@xxxxxxxxxxxxx> wrote:
> commit 3d9545cc375d117554a9b35dfddadf9189c62775
> Author: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Date:   Mon Apr 23 13:54:36 2012 -0400
>    EHCI: maintain the ehci->command value properly
>    The ehci-hcd driver is a little haphazard about keeping track of the
>    state of the USBCMD register.  The ehci->command field is supposed to
>    hold the register's value (apart from a few special bits) at all
>    times, but it isn't maintained properly.
>    This patch (as1543) cleans up the situation.  It keeps ehci->command
>    up-to-date, and uses that value rather than reading the register from
>    the hardware whenever possible.
>    Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> The above commit causes failure of imx usb host hub detection.

This commit may introduce an overriding problem on initial configuration
of CMD: initial configuration of CMD is figured out in ehci_init, but is
override later in the following ehci_reset, see ehci_setup.

So could you please try the below patch to see if it can fix your problem?

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index f644ba9..29a9057 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -318,8 +318,7 @@ static void tdi_reset (struct ehci_hcd *ehci)
 	ehci_writel(ehci, tmp, reg_ptr);

-/* reset a non-running (STS_HALT == 1) controller */
-static int ehci_reset (struct ehci_hcd *ehci)
+static int __ehci_reset (struct ehci_hcd *ehci)
 	int	retval;
 	u32	command = ehci_readl(ehci, &ehci->regs->command);
@@ -352,12 +351,27 @@ static int ehci_reset (struct ehci_hcd *ehci)
 	if (ehci->debug)

-	ehci->command = ehci_readl(ehci, &ehci->regs->command);
 	ehci->port_c_suspend = ehci->suspended_ports =
 			ehci->resuming_ports = 0;
 	return retval;

+/* ehci hardware init */
+static int ehci_hw_init (struct ehci_hcd *ehci)
+	return __ehci_reset(ehci);
+/* reset a non-running (STS_HALT == 1) controller */
+static int ehci_reset (struct ehci_hcd *ehci)
+	int val;
+	val =  __ehci_reset(ehci);
+	ehci->command = ehci_readl(ehci, &ehci->regs->command);
+	return val;
 /* idle the controller (from running) */
 static void ehci_quiesce (struct ehci_hcd *ehci)
@@ -836,7 +850,7 @@ static int __maybe_unused ehci_setup (struct usb_hcd *hcd)
 	if (retval)
 		return retval;

-	ehci_reset(ehci);
+	ehci_hw_init(ehci);

 	return 0;

Ming Lei
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