Re: [PATCH] [RFT] sh: mach-r2d: Handle virq offset in cascaded IRL demux

[John Paul Adrian Glaubitz]

Hi Geert!

On Sun, 2023-07-09 at 13:15 +0200, Geert Uytterhoeven wrote:
> When booting rts7751r2dplus_defconfig on QEMU, the system hangs due to
> an interrupt storm on IRQ 20.  IRQ 20 aka event 0x280 is a cascaded IRL
> interrupt, which maps to IRQ_VOYAGER, the interrupt used by the Silicon
> Motion SM501 multimedia companion chip.  As rts7751r2d_irq_demux() does
> not take into account the new virq offset, the interrupt is no longer
> translated, leading to an unhandled interrupt.
> 
> Fix this by taking into account the virq offset when translating
> cascaded IRL interrupts.
> 
> Fixes: a8ac2961148e8c72 ("sh: Avoid using IRQ0 on SH3 and SH4")
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Closes: https://lore.kernel.org/r/fbfea3ad-d327-4ad5-ac9c-648c7ca3fe1f@xxxxxxxxxxxx
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> Highlander and Dreamcast probably have the same issue.
> I'll send patches for these later...
> ---
>  arch/sh/boards/mach-r2d/irq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/sh/boards/mach-r2d/irq.c b/arch/sh/boards/mach-r2d/irq.c
> index e34f81e9ae813b8d..c37b40398c5bc83e 100644
> --- a/arch/sh/boards/mach-r2d/irq.c
> +++ b/arch/sh/boards/mach-r2d/irq.c
> @@ -117,10 +117,10 @@ static unsigned char irl2irq[R2D_NR_IRL];
>  
>  int rts7751r2d_irq_demux(int irq)
>  {
> -	if (irq >= R2D_NR_IRL || irq < 0 || !irl2irq[irq])
> +	if (irq >= 16 + R2D_NR_IRL || irq < 16 || !irl2irq[irq - 16])
>  		return irq;
>  
> -	return irl2irq[irq];
> +	return irl2irq[irq - 16];
>  }
>  
>  /*

Funny, this is actually almost what I did myself when trying to fix this
issue. Only difference was that I applied the offset of 16 only to one
of the instances at a time and it never occurred to me that it needs to
be applied to all instances.

Thanks for fixing this!

Reviewed-by: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913