Message-ID: <495933D6.1020409@tragetaschen.dyndns.org>
Date: Mon, 29 Dec 2008 21:32:22 +0100
From: Kai Ruhnau <kai@tragetaschen.dyndns.org>
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To: LKML <linux-kernel@vger.kernel.org>
Subject: System hang in quirk_usb_handoff_ohci
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Hi,

Some days ago, I reported a reproducible hang during boot. The
information around was quite vague and so I took the liberty to further
dig into the the call stack of pci_init and found the exact place where
the initialization locks.
But first the symptoms (those are improved as well):

If I turn on or restart my computer and try to boot without my
intervention, the system always hangs during boot, the last output being
the io scheduler registration. However, if I press a key at any time
after the BIOS (for example manual choosing  the grub entry or during
the kernel messages) the system happily boots normally.

After a little printk debugging, it turns out, that
quirk_usb_handoff_ohci will hang when applied to my first USB OHCI pci
device. I have marked the offending line in the following snippet (line
186 in the original---the second writel)

============ (startint at line 182 inn pci-quirks.c)
[...]
    u32 control = readl(base + OHCI_CONTROL);
    if (control & OHCI_CTRL_IR) {
        int wait_time = 500; /* arbitrary; 5 seconds */
        writel(OHCI_INTR_OC, base + OHCI_INTRENABLE);

       // The next line might hang

        writel(OHCI_OCR, base + OHCI_CMDSTATUS);
        while (wait_time > 0 &&
                readl(base + OHCI_CONTROL) & OHCI_CTRL_IR) {
            wait_time -= 10;
            msleep(10);
        }
[...]
=========

The lspci output for the device is

00:13.0 0c03: 1002:4387 (prog-if 10 [OHCI])
        Subsystem: 1462:7326              
        Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 16
        Memory at fdffe000 (32-bit, non-prefetchable) [size=4K]   
        Kernel driver in use: ohci_hcd                            
        Kernel modules: ohci-hcd                                  

My system is a

Linux  2.6.28-gentoo #12 SMP PREEMPT Mon Dec 29 21:01:04 CET 2008 x86_64
Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz GenuineIntel GNU/Linux

Thanks for your time.

Best regards
Kai

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