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

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Date:   Mon, 13 Dec 2021 16:10:14 +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 Thu, 09 Dec 2021 04:32:48 +0000,
Hector Martin <marcan@...can.st> wrote:
> 
> Multi-die support in AICv2 uses several sets of IRQ registers. Introduce
> a die count and compute the register group offset based on the die ID
> field of the hwirq number, as reported by the hardware.
> 
> Signed-off-by: Hector Martin <marcan@...can.st>
> ---
>  drivers/irqchip/irq-apple-aic.c | 75 +++++++++++++++++++++++----------
>  1 file changed, 53 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
> index d03caed51d56..46b7750548a0 100644
> --- a/drivers/irqchip/irq-apple-aic.c
> +++ b/drivers/irqchip/irq-apple-aic.c

[...]

> @@ -535,28 +545,41 @@ static int aic_irq_domain_translate(struct irq_domain *id,
>  				    unsigned int *type)
>  {
>  	struct aic_irq_chip *ic = id->host_data;
> +	u32 *args;
> +	u32 die = 0;
>  
> -	if (fwspec->param_count != 3 || !is_of_node(fwspec->fwnode))
> +	if (fwspec->param_count < 3 || fwspec->param_count > 4 ||
> +	    !is_of_node(fwspec->fwnode))
>  		return -EINVAL;
>  
> +	args = &fwspec->param[1];
> +
> +	if (fwspec->param_count == 4) {
> +		die = args[0];
> +		args++;
> +	}
> +
>  	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)

Thanks,

	M.

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