linux-kernel - Re: [PATCH v3] sh: avoid using IRQ0 on SH3/4

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Date:   Tue, 3 May 2022 08:58:22 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Rob Landley <rob@...dley.net>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3] sh: avoid using IRQ0 on SH3/4

Hi Sergey,

On Mon, May 2, 2022 at 10:56 PM Sergey Shtylyov <s.shtylyov@....ru> wrote:
> On 5/2/22 11:37 AM, Geert Uytterhoeven wrote:
> >>>> Using IRQ0 by the platform devices is going to be disallowed soon (see [1])
> >>>> and even now, when IRQ0 is about to be returned by platfrom_get_irq(), you
> >>>> see a big warning.  The code supporting SH3/4 SoCs 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 use IRQ0 for the SMSC911x compatible Ethernet chip...
> >
> >> As I told him in IRC, the problem is still that sh4 never gives me a shell
> >> prompt with this patch applied. I just reconfirmed it against current git:
> >>
> >> Freeing unused kernel image (initmem) memory: 124K
> >> This architecture does not have kernel memory protection.
> >> Run /init as init process
> >> mountpoint: dev/pts: No such file or directory
> >> 8139cp 0000:00:02.0 eth0: link up, 100Mbps, full-duplex, lpa 0x05E1
> >>
> >> It makes it partway through the init script, but it hangs with qemu-system-sh4
> >> stuck in a CPU-eating loop before finishing. Without the patch, I get a shell
> >> prompt.
> >
> > I regularly test on qemu rts7751r2d, but couldn't produce your
> > issue.  Until I tried "ifconfig eth0 up", which causes a lock-up.
> > Interestingly, the 8139 irq was 112 with and without Sergey's patch,
> > so there must be an irq remapping missing.
> >
> > I also test regularly on landisk, where 8139 Ethernet works fine.
> > Turns out landisk uses arch/sh/drivers/pci/fixups-landisk.c to fixup
> > the irq...
> >
> > arch/sh/include/mach-common/mach/r2d.h has:
> > #define R2D_FPGA_IRQ_BASE       100
> > Subtracting 16 here does not help.
>
>    Why subtract when you contrariwise need to add? :-)

Thanks, adding 16 here fixed the issue:

/ # ifconfig eth0 up
8139cp 0000:00:02.0 eth0: link up, 100Mbps, full-duplex, lpa 0x05E1

> > With this (gmail-whitespace-damaged) patch:
> >
> > --- a/arch/sh/drivers/pci/fixups-rts7751r2d.c
> > +++ b/arch/sh/drivers/pci/fixups-rts7751r2d.c
> > @@ -31,9 +31,9 @@ static char lboxre2_irq_tab[] = {
> >  int pcibios_map_platform_irq(const struct pci_dev *pdev, u8 slot, u8 pin)
> >  {
> >         if (mach_is_lboxre2())
> > -               return lboxre2_irq_tab[slot];
> > +               return lboxre2_irq_tab[slot] - 16;
>
>    This table contains the values #define'd via evt2irq(), so
> shouldn't need to subtract anything...
>
> >         else
> > -               return rts7751r2d_irq_tab[slot];
> > +               return rts7751r2d_irq_tab[slot] - 16;
>
>    How about + 16?

Doesn't work, but changing R2D_FPGA_IRQ_BASE does work, see
above.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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