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

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Message-ID: <d9f96032-c20c-beb0-feba-a66a9b17af0c@marcan.st>
Date:   Sat, 18 Dec 2021 14:39:04 +0900
From:   Hector Martin <marcan@...can.st>
To:     Marc Zyngier <maz@...nel.org>
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 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.

-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub