linux-kernel - Re: m68k: Convert to genirq (WIP)

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Date:	Wed, 10 Aug 2011 20:53:16 +1000 (EST)
From:	Finn Thain <fthain@...egraphics.com.au>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
cc:	Brad Boyer <flar@...andria.com>,
	Linux/m68k <linux-m68k@...ts.linux-m68k.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>
Subject: Re: m68k: Convert to genirq (WIP)


On Wed, 10 Aug 2011, Geert Uytterhoeven wrote:
> 
> While looking into optimizing interrupts using chain handlers (which 
> cannot be shared), I noticed several of these cascades are hung on the 
> same interrupt. Hence we cannot use the optimization of chain handlers 
> for them.
> 
> Knowing which are mutually exclusive helps a lot, but my Mac knowledge 
> is very limited.
> 
> I derived from the code this list of cascade handlers and the interrupts 
> they use:
> 
> baboon_irq
>     IRQ_NUBUS_C
> 
> oss_irq
>     OSS_IRQLEV_SCSI = IRQ_AUTO_2                conflict: via2_irq
>     OSS_IRQLEV_SOUND = IRQ_AUTO_5               conflict: psc_irq

PSC and OSS are mutually exclusive.

VIA2 and OSS are also mutually exlusive.

> 
> oss_nubus_irq
>     OSS_IRQLEV_NUBUS = IRQ_AUTO_3               conflict: psc_irq
> 
> psc_irq
>     IRQ_AUTO_3                                  conflict: oss_nubus_irq
>     IRQ_AUTO_4
>     IRQ_AUTO_5                                  conflict: oss_irq
>     IRQ_AUTO_6                                  conflict: via1_irq
> 
> via1_irq
>     OSS_IRQLEV_VIA1 = IRQ_AUTO_6 (on oss)       conflict: psc_irq
> 
>     IRQ_AUTO_1                                  conflict: iop_ism_irq

iop_ism_irq is only used with OSS.

>     IRQ_AUTO_6 (if via_alt_mapping)             conflict: psc_irq

via_alt_mapping is not used with PSC.

> 
> via2_irq
>     IRQ_AUTO_2                                  conflict: oss_irq
> 
> via_nubus_irq
>     IRQ_MAC_NUBUS = IRQ_VIA2_1
> 
> These are other interrupts using in the Mac core code, which may use the same
> interrupts as some of the cascades above:
> 
> iop_ism_irq
>     OSS_IRQLEV_IOPISM = 1 = IRQ_AUTO_1 (on oss) conflict: via1_irq

via1_irq is remapped to IRQ_AUTO_6 on OSS.

>     IRQ_VIA2_0 (on !oss)
> 
> mac_nmi_handler
>     IRQ_AUTO_7
> 
> timer handler
>     IRQ_MAC_TIMER_1 = IRQ_VIA1_6
> 
> So baboon and PSC are mutually exclusive? But they don't conflict w.r.t. to
> interrupt lines anyway, so they're not an issue.
> 
> From the code, OSS and VIA are also mutually exclusive (except for via1_irq)?
> 
> But PSC can coexist with OSS? That's where most of the conflicts are.

Hope this helps...

Finn

> 
> 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
>