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

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Date:   Mon, 2 May 2022 10:37:00 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Rob Landley <rob@...dley.net>
Cc:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        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 Rob,

On Sat, Apr 30, 2022 at 3:52 PM Rob Landley <rob@...dley.net> wrote:
> On 4/29/22 09:24, John Paul Adrian Glaubitz wrote:
> > On 4/27/22 20:46, Sergey Shtylyov 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.

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;
        else
-               return rts7751r2d_irq_tab[slot];
+               return rts7751r2d_irq_tab[slot] - 16;
 }

 int pci_fixup_pcic(struct pci_channel *chan)

it no longer crashes, but ifconfig still fails:

/ # ifconfig eth0 up
ifconfig: ioctl 0x8914 failed: Invalid argument

Note that there are more implementations of pcibios_map_platform_irq()
that do not use evt2irq(), and thus are probably broken by this patch.

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