linux-kernel - Re: [PATCH 5/6] irqchip/apple-aic: Support multiple dies

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Date:   Mon, 20 Dec 2021 13:38:16 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 5/6] irqchip/apple-aic: Support multiple dies

On Sat, 18 Dec 2021 05:39:04 +0000,
Hector Martin <marcan@...can.st> wrote:
> 
> On 14/12/2021 01.10, Marc Zyngier wrote:
> >>  	switch (fwspec->param[0]) {
> >>  	case AIC_IRQ:
> >> -		if (fwspec->param[1] >= ic->nr_irq)
> >> +		if (die >= ic->nr_die)
> >> +			return -EINVAL;
> >> +		if (args[0] >= ic->nr_irq)
> >>  			return -EINVAL;
> >> -		*hwirq = (FIELD_PREP(AIC_EVENT_TYPE, AIC_EVENT_TYPE_HW) |
> >> -			  FIELD_PREP(AIC_EVENT_NUM, fwspec->param[1]));
> >> +		*hwirq = AIC_IRQ_HWIRQ(die, args[0]);
> >>  		break;
> > 
> > A side issue with this is that it breaks MSIs, due to the way we
> > construct the intspec (I did hit that when upgrading the M1 intspec to
> > 4 cells for the PMU). I have the following hack locally:
> > 
> > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> > index b090924b41fe..f7b4a67b13cf 100644
> > --- a/drivers/pci/controller/pcie-apple.c
> > +++ b/drivers/pci/controller/pcie-apple.c
> > @@ -218,7 +218,7 @@ static int apple_msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
> >  	if (hwirq < 0)
> >  		return -ENOSPC;
> >  
> > -	fwspec.param[1] += hwirq;
> > +	fwspec.param[1 + (fwspec.param_count == 4)] += hwirq;
> >  
> >  	ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, &fwspec);
> >  	if (ret)
> > 
> 
> Heh, I never noticed; probably because I guess the SD card reader on the
> machine I've been testing this on doesn't use MSIs, and I haven't tried
> WiFi yet.
> 
> Perhaps (fwspec.param_count - 2)? It's probably a safer long-term
> assumption that the last two cells will always be leaf IRQ number and type.

Yup, that'd work as well, as long as we make this assumption explicit.

	M.

-- 
Without deviation from the norm, progress is not possible.