Date:	Mon, 13 Oct 2014 09:56:20 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	"Joe.C" <yingjoe.chen@...iatek.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>
CC:	"arm@...nel.org" <arm@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"srv_heupstream@...iatek.com" <srv_heupstream@...iatek.com>,
	"yingjoe.chen@...il.com" <yingjoe.chen@...il.com>,
	"hc.yen@...iatek.com" <hc.yen@...iatek.com>,
	"eddie.huang@...iatek.com" <eddie.huang@...iatek.com>,
	"nathan.chung@...iatek.com" <nathan.chung@...iatek.com>,
	"yh.chen@...iatek.com" <yh.chen@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Pawel Moll <Pawel.Moll@....com>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Matt Porter <mporter@...aro.org>,
	Marc Carino <marc.ceeeee@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Sricharan R <r.sricharan@...com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/7] irqchip: gic: Support hierarchy irq domain.

On 09/10/14 15:29, Joe.C wrote:
> From: "Joe.C" <yingjoe.chen@...iatek.com>
> 
> Add support to use gic as a parent for stacked irq domain.
> 
> Signed-off-by: Joe.C <yingjoe.chen@...iatek.com>
> ---
>  drivers/irqchip/irq-gic.c | 56 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 48 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index dda6dbc..17f5aa6 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -767,19 +767,17 @@ void __init gic_init_physaddr(struct device_node *node)
>  static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
>  				irq_hw_number_t hw)
>  {
> +	irq_domain_set_hwirq_and_chip(d, irq, hw, &gic_chip, d->host_data);
>  	if (hw < 32) {
>  		irq_set_percpu_devid(irq);
> -		irq_set_chip_and_handler(irq, &gic_chip,
> -					 handle_percpu_devid_irq);
> +		irq_set_handler(irq, handle_percpu_devid_irq);
>  		set_irq_flags(irq, IRQF_VALID | IRQF_NOAUTOEN);
>  	} else {
> -		irq_set_chip_and_handler(irq, &gic_chip,
> -					 handle_fasteoi_irq);
> +		irq_set_handler(irq, handle_fasteoi_irq);
>  		set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
>  
>  		gic_routable_irq_domain_ops->map(d, irq, hw);
>  	}
> -	irq_set_chip_data(irq, d->host_data);
>  	return 0;
>  }
>  
> @@ -795,8 +793,6 @@ static int gic_irq_domain_xlate(struct irq_domain *d,
>  {
>  	unsigned long ret = 0;
>  
> -	if (d->of_node != controller)
> -		return -EINVAL;
>  	if (intsize < 3)
>  		return -EINVAL;
>  
> @@ -839,6 +835,46 @@ static struct notifier_block gic_cpu_notifier = {
>  };
>  #endif
>  
> +
> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> +static int gic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> +				unsigned int nr_irqs, void *arg)
> +{
> +	int i, ret;
> +	irq_hw_number_t hwirq;
> +	unsigned int type = IRQ_TYPE_NONE;
> +	struct of_phandle_args *irq_data = arg;
> +
> +	ret = gic_irq_domain_xlate(domain, irq_data->np, irq_data->args,
> +				   irq_data->args_count, &hwirq, &type);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < nr_irqs; i++)
> +		gic_irq_domain_map(domain, virq+i, hwirq+i);
> +
> +	return 0;
> +}
> +
> +static void gic_irq_domain_free(struct irq_domain *domain, unsigned int virq,
> +				unsigned int nr_irqs)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		irq_set_handler(virq + i, NULL);
> +		irq_domain_set_hwirq_and_chip(domain, virq + i, 0, NULL, NULL);
> +	}
> +}
> +
> +static const struct irq_domain_ops gic_irq_domain_hierarchy_ops = {
> +	.alloc = gic_irq_domain_alloc,
> +	.free = gic_irq_domain_free,
> +};
> +#else
> +#define gic_irq_domain_hierarchy_ops 0
> +#endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */
> +
>  static const struct irq_domain_ops gic_irq_domain_ops = {
>  	.map = gic_irq_domain_map,
>  	.unmap = gic_irq_domain_unmap,
> @@ -952,7 +988,11 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
>  
>  	gic_irqs -= hwirq_base; /* calculate # of irqs to allocate */
>  
> -	if (of_property_read_u32(node, "arm,routable-irqs",
> +	if (IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) &&
> +		of_find_property(node, "arm,irq-domain-hierarchy", NULL))
> +		gic->domain = irq_domain_add_linear(node, gic_irqs,
> +					&gic_irq_domain_hierarchy_ops, gic);
> +	else if (of_property_read_u32(node, "arm,routable-irqs",
>  				 &nr_routable_irqs)) {
>  		irq_base = irq_alloc_descs(irq_start, 16, gic_irqs,
>  					   numa_node_id());
> 

So I've been playing with this over the weekend (with quite a few
tweaks), and I'm hitting a not-so-nice effect of the automatic platform
device creation from the device tree.

What happens is the following:
- Kernel starts
- GIC gets initialized with a linear domain supporting hierarchy
- per-cpu timers are up and running
- platform devices get created from the device tree:
  - irq_of_parse_and_map()
  - irq_create_of_mapping()
  - irq_domain_alloc_irqs()

Here, we start re-allocating interrupts that have already been allocated
(the timer interrupts). This has a side effect of nuking the
percpu_dev_id, and everything explodes on the next timer tick. Grmbl.

The main issue here is that we have a single path that:
- translates the interrupt from DT to HW
- configures the interrupts
and that we use it more than once.

The non-hierarchy path works because the the "map" operation takes place
only once, and virtual interrupts are allocated upfront.

When we switch to this more dynamic way of doing things, the fact that
the virqs only available at allocation time is screwing us up.

I can see a way out of this, which would involve having a way of
detecting that a hwirq has already been allocated (which requires having
the xlate callback instantiated). Something like this (not even
compile-tested):

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index dd8d3ab..6a45821 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -479,6 +479,21 @@ unsigned int irq_create_of_mapping(struct
of_phandle_args *irq_data)
 	}

 	if (irq_domain_is_hierarchy(domain)) {
+		if (domain->ops->xlate) {
+			/*
+			 * If we've already configured this interrupt,
+			 * don't do it again, or hell will break loose.
+			 */
+			if (domain->ops->xlate(domain, irq_data->np,
+					       irq_data->args,
+					       irq_data->args_count,
+					       &hwirq, &type))
+				return 0;
+
+			virq = irq_find_mapping(domain, hwirq);
+			if (virq)
+				return virq;
+		}
 		virq = irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, irq_data);
 		return virq <= 0 ? 0 : virq;
 	}

Thoughts?

	M.
-- 
Jazz is not dead. It just smells funny...

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