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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 18 Feb 2021 16:38:40 +0100
Message-ID: <CAMuHMdVD+BhxXcmZYvVK5QgtNsmbgyzS_Yx+dbFYmN8xdw0kDA@mail.gmail.com>
Subject: Re: [RFC] IRQ handlers run with some high-priority interrupts(not
 NMI) enabled on some platform
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Finn Thain <fthain@telegraphics.com.au>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "funaho@jurai.org" <funaho@jurai.org>,
        "philb@gnu.org" <philb@gnu.org>, "corbet@lwn.net" <corbet@lwn.net>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "linux-m68k@lists.linux-m68k.org" <linux-m68k@lists.linux-m68k.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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Hi Arnd,

On Thu, Feb 18, 2021 at 2:59 PM Arnd Bergmann <arnd@kernel.org> wrote:
> On Thu, Feb 18, 2021 at 1:30 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > The reason drivers/ide is doing that may be related to IDE hard drive
> > quirks.  The old WD Caviar drives didn't obey disabling the IDE interrupt
> > at the drive level.  On PC, that worked fine, as IRQs 14 and 15 weren't
> > shared with other devices.  On systems with shared interrupts, that
> > broke badly, and led to an interrupt storm.
>
> So presumably anyone that has one of those old drives will not be
> able to move to drivers/ata then? I see that drivers/ata doesn't do
> the transfers in interrupt mode, so it would seem to rely on masking
> at the device level.

I don't know.  This was an issue I debugged on a friend's Amiga in 1995
or so ;-)  All bad WD Caviars may have died in the meantime...

BTW, it wouldn't be the first time a drive quirk handling wasn't ported
from drivers/ide/ to drivers/ata/.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds