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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Fri, 7 Jul 2023 07:34:41 -0700
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To:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
        Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Sergey Shtylyov <s.shtylyov@omp.ru>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, linux-sh@vger.kernel.org,
        linux-kernel@vger.kernel.org
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From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] sh: Avoid using IRQ0 on SH3 and SH4
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On 7/7/23 02:53, John Paul Adrian Glaubitz wrote:
> Hi Geert!
> 
> On Fri, 2023-07-07 at 10:48 +0200, Geert Uytterhoeven wrote:
>>> I can reproduce the issue with rts7751r2dplus_defconfig, but I may
>>> not be able to look into it today...
>>
>> Disabling CONFIG_USB_OHCI_HCD fixes the hang.
> 
> I picked rts7751r2dplus_defconfig, disabled CONFIG_USB_OHCI_HCD but it still
> hangs for me. Are you sure it's CONFIG_USB_OHCI_HCD and not something else?
> 

It seems to be related. With this patch reverted, ohci_irq() gets a single
interrupt, and boot continues. With this patch in place, ohci_irq() does
not get any interrupts, and boot hangs with qemu at 100% CPU. I confirmed
this by disabling CONFIG_MFD_SM501. After that, the hang is no longer seen.
Of course, that also means that OHCI and other emulated sm501 functionality
no longer works.

My suspicion is that something goes wrong with interrupt routing to
SM501 and with it to ohci_irq(), but that is just a wild guess.

Guenter