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SubjectRe: [ 011/108] powerpc/usb: fix bug of kernel hang when initializing usb
Greg KH <> writes:

> 3.0-stable review patch. If anyone has any objections, please let me know.
> ------------------
> From: Shengzhou Liu <>
> commit 28c56ea1431421dec51b7b229369e991481453df upstream.
> If USB UTMI PHY is not enable, writing to portsc register will lead to
> kernel hang during boot up.

I apologize for the late response, but I was encountering this same
hang (on an 8315) and applied this patch. (For what it's worth, I'm
only seeing it after many warm boots; a cold boot / hard power cycle
solves the issue, but since this is eventually going to be locked up
in a box without a console...)

I encountered the hang again this evening, so this fix (plus the snoop
fix) is not sufficientl

Reading through the original thread, it seems that an additional delay
might be required:

> First, the SDK kernel had a delay after setting that bit, I added
> that back in. This is not what fixed it but it looks like the
> right thing to do, though please, use msleep rather than udelay
> here if possible (not in atomic context).

However, I never saw a patch to that effect. I'm assuming (hoping!)
it's something as simple as:

diff --git a/drivers/usb/host/ehci-fsl.c b/drivers/usb/host/ehci-fsl.c
index 09fd214..d58c1c6 100644
--- a/drivers/usb/host/ehci-fsl.c
+++ b/drivers/usb/host/ehci-fsl.c
@@ -236,6 +236,7 @@ static void ehci_fsl_setup_phy(struct ehci_hcd *ehci,
/* enable UTMI PHY */
setbits32(non_ehci + FSL_SOC_USB_CTRL, CTRL_UTMI_PHY_EN);
+ msleep(5);
portsc |= PORT_PTS_UTMI;

But confirmation would be nice. Also, which SDK kernel was this
compared against? I just downloaded the 8315ERDB BSP, and the kernel
there doesn't seem to have any of this in it.

There was also the follow-on patch that enabled snooping (to deal with
cache coherency?):

(If there was a formal patch there, it looks like it got scrambled on
gmane, and I can't find another list archive.)
Is that also needed for consistent results here? (Or are we wandering
astray from "-stable" material?)


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