linux-kernel - Re: [PATCH] sh: Avoid using IRQ0 on SH3 and SH4

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Date:   Thu, 6 Jul 2023 08:51:29 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sh: Avoid using IRQ0 on SH3 and SH4

On 7/6/23 07:01, John Paul Adrian Glaubitz wrote:
> Hi Guenter!
> 
> On Thu, 2023-07-06 at 06:57 -0700, Guenter Roeck wrote:
>> On Thu, Jun 01, 2023 at 11:22:17PM +0300, Sergey Shtylyov wrote:
>>> IRQ0 is no longer returned by platform_get_irq() and its ilk -- they now
>>> return -EINVAL instead.  However, the kernel code supporting SH3/4-based
>>> SoCs still maps the IRQ #s starting at 0 -- modify that code to start the
>>> IRQ #s from 16 instead.
>>>
>>> The patch should mostly affect the AP-SH4A-3A/AP-SH4AD-0A boards as they
>>> indeed are using IRQ0 for the SMSC911x compatible Ethernet chip.
>>>
>>
>> Unfortunately it also affects all sh4 emulations in qemu, and results in
>> boot stalls with those. There isn't a relevant log to attach because there
>> is no error message - booting just stalls until the emulation is aborted.
>>
>> Reverting this patch fixes the problem.
>>
>> Bisect log is attached for reference. Note that bisect requires applying
>> commit 7497840d462c ("sh: Provide unxlate_dev_mem_ptr() in asm/io.h"),
>> which is also the reason why the problem was not observed earlier since
>> it was hiding behind a build failure.
> 
> Interesting. My naive understanding was that IRQ0 is no longer usable in the
> kernel as Sergey claimed. Was that not correct?
> 

I have no idea. All I know is that all my sh4 qemu emulations hang during boot
after this patch is applied. I don't have CONFIG_SMSC911X enabled in my builds.
I also don't see any error messages from failed IRQ requests after reverting
this patch.

Guenter