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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 9 Feb 2022 17:02:47 +0100
Message-ID: <CAK8P3a0gf6TeK2vZ+u3NZ2VrrvrGUohAPz5WiZ4Mbk5QQg9FFg@mail.gmail.com>
Subject: Re: [PATCH 2/3] i2c: sh_mobile: Use platform_get_irq_optional() to
 get the interrupt
To:     Sergei Shtylyov <sergei.shtylyov@gmail.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Rob Herring <robh+dt@kernel.org>,
        Nicolas Saenz Julienne <nsaenz@kernel.org>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
        Chris Brandt <chris.brandt@renesas.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Linux I2C <linux-i2c@vger.kernel.org>,
        linux-rpi-kernel <linux-rpi-kernel@lists.infradead.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Prabhakar <prabhakar.csengg@gmail.com>,
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On Wed, Feb 9, 2022 at 4:48 PM Sergei Shtylyov
<sergei.shtylyov@gmail.com> wrote:
> On 2/9/22 6:18 PM, Arnd Bergmann wrote:
> >>> since 2009 after 1e1030dccb10 ("sh: nmi_debug support."). On a
> >>
> >>    Mhm... this commit changes the SH3 code while SH778x are SH4A, no?
> >
> > This code is shared between both:
> >
> > arch/sh/kernel/cpu/sh4/Makefile:common-y        += $(addprefix
> > ../sh3/, entry.o ex.o)
>
>    Ah, quite convoluted! :-)
>    So you mean thet broke the delivery of EVT 0x200 when mucking with NMI?

Yes, exactly: If I read this right, the added code:

+       shlr2   r4
+       shlr    r4
+       mov     r4, r0          ! save vector->jmp table offset for later
+
+       shlr2   r4              ! vector to IRQ# conversion
+       add     #-0x10, r4
+
+       cmp/pz  r4              ! is it a valid IRQ?
+       bt      10f

gets the vector (0x200 for this device), shifts it five bits to 0x10,
and subtracts 0x10,
then branches to do_IRQ if the interrupt number is non-zero, otherwise it goes
through the exception_handling_table.

         Arnd