linux-kernel - Re: [PATCH V2 03/19] irqchip: crossbar: Skip some irqs from getting mapped to crossbar

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Date:	Thu, 12 Jun 2014 18:49:17 +0530
From:	Sricharan R <r.sricharan@...com>
To:	Jason Cooper <jason@...edaemon.net>
CC:	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<tony@...mide.com>, <santosh.shilimkar@...com>, <nm@...com>,
	<rnayak@...com>, <linux@....linux.org.uk>, <tglx@...utronix.de>
Subject: Re: [PATCH V2 03/19] irqchip: crossbar: Skip some irqs from getting
 mapped to crossbar

Hi Jason,

On Thursday 12 June 2014 06:21 PM, Jason Cooper wrote:
> On Thu, Jun 12, 2014 at 05:23:11PM +0530, Sricharan R wrote:
>> From: Nishanth Menon <nm@...com>
>>
>> When, in the system due to varied reasons, interrupts might be unusable
>> due to hardware behavior, but register maps do exist, then those interrupts
>> should be skipped while mapping irq to crossbars.
>>
>> Signed-off-by: Nishanth Menon <nm@...com>
>> Signed-off-by: Sricharan R <r.sricharan@...com>
>> Signed-off-by: Tony Lindgren <tony@...mide.com>
> 
> Tony, have you applied these somewhere already?
> 
>> ---
>>  drivers/irqchip/irq-crossbar.c |   47 ++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 43 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/irqchip/irq-crossbar.c b/drivers/irqchip/irq-crossbar.c
>> index 51d4b87..847f6e3 100644
>> --- a/drivers/irqchip/irq-crossbar.c
>> +++ b/drivers/irqchip/irq-crossbar.c
>> @@ -13,11 +13,13 @@
>>  #include <linux/io.h>
>>  #include <linux/of_address.h>
>>  #include <linux/of_irq.h>
>> +#include <linux/of_device.h>
>>  #include <linux/slab.h>
>>  #include <linux/irqchip/arm-gic.h>
>>  
>>  #define IRQ_FREE	-1
>>  #define IRQ_RESERVED	-2
>> +#define IRQ_SKIP	-3
>>  #define GIC_IRQ_START	32
>>  
>>  /*
>> @@ -34,6 +36,16 @@ struct crossbar_device {
>>  	void (*write) (int, int);
>>  };
>>  
>> +/**
>> + * struct crossbar_data: Platform specific data
>> + * @irqs_unused: array of irqs that cannot be used because of hw erratas
>> + * @size: size of the irqs_unused array
>> + */
>> +struct crossbar_data {
>> +	const uint *irqs_unused;
>> +	const uint size;
>> +};
>> +
>>  static struct crossbar_device *cb;
>>  
>>  static inline void crossbar_writel(int irq_no, int cb_no)
>> @@ -119,10 +131,12 @@ const struct irq_domain_ops routable_irq_domain_ops = {
>>  	.xlate = crossbar_domain_xlate
>>  };
>>  
>> -static int __init crossbar_of_init(struct device_node *node)
>> +static int __init crossbar_of_init(struct device_node *node,
>> +				   const struct crossbar_data *data)
>>  {
>>  	int i, size, max, reserved = 0, entry;
>>  	const __be32 *irqsr;
>> +	const int *irqsk = NULL;
>>  
>>  	cb = kzalloc(sizeof(*cb), GFP_KERNEL);
>>  
>> @@ -194,6 +208,22 @@ static int __init crossbar_of_init(struct device_node *node)
>>  		reserved += size;
>>  	}
>>  
>> +	/* Skip the ones marked as unused */
>> +	if (data) {
>> +		irqsk = data->irqs_unused;
>> +		size = data->size;
>> +
>> +		for (i = 0; i < size; i++) {
>> +			entry = irqsk[i];
>> +
>> +			if (entry > max) {
>> +				pr_err("Invalid skip entry\n");
>> +				goto err3;
>> +			}
>> +			cb->irq_map[entry] = IRQ_SKIP;
>> +		}
>> +	}
>> +
>>  	register_routable_domain_ops(&routable_irq_domain_ops);
>>  	return 0;
>>  
>> @@ -208,18 +238,27 @@ err1:
>>  	return -ENOMEM;
>>  }
>>  
>> +/* irq number 10 cannot be used because of hw bug */
>> +int dra_irqs_unused[] = { 10 };
>> +struct crossbar_data cb_dra_data = { dra_irqs_unused,
>> +				     ARRAY_SIZE(dra_irqs_unused) };
>> +
>>  static const struct of_device_id crossbar_match[] __initconst = {
>> -	{ .compatible = "ti,irq-crossbar" },
>> +	{ .compatible = "ti,irq-crossbar", .data = &cb_dra_data },
>>  	{}
>>  };
> 
> This is a bug in all implementations of this IP?  Or, a specific
> SoC's implementation?  Would this be better expressed in the dts via a
> property?  Can we expect future implementations to be fixed?
> 
> thx,
> 
> Jason.
 Infact this and PATCH#10 should be merged. I will change that.

 So in Socs's (2 so far) that do have a crossbar, some irqs are mapped
 through a crossbar and some are directly wired to the irqchip.
 These 'unused irqs' are those which are directly wired but they still
 have a crossbar register. Their routing cannot be changed. So this
 is not really expected usage of the crossbar hw ip. We initially thought
 having a dts property separately for this, but took this path to avoid
 loading the dts with additional bindings which may not be generic.

Regards,
 Sricharan 
 
 
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