linux-kernel - Re: [PATCH V2 16/19] irqchip: crossbar: introduce ti,max-crossbar-sources to identify valid crossbar mapping

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Date:	Fri, 13 Jun 2014 16:24:52 +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 16/19] irqchip: crossbar: introduce ti,max-crossbar-sources
 to identify valid crossbar mapping

Hi Jason,

On Thursday 12 June 2014 07:24 PM, Jason Cooper wrote:
> On Thu, Jun 12, 2014 at 05:23:24PM +0530, Sricharan R wrote:
>> From: Nishanth Menon <nm@...com>
>>
>> Currently we attempt to map any crossbar value to an IRQ, however,
>> this is not correct from hardware perspective. There is a max crossbar
>> event number upto which hardware supports. So describe the same in
>> device tree using 'ti,max-crossbar-sources' property and use it to
>> validate requests.
>>
>> Signed-off-by: Nishanth Menon <nm@...com>
>> ---
>>  .../devicetree/bindings/arm/omap/crossbar.txt      |    2 ++
>>  drivers/irqchip/irq-crossbar.c                     |   21 ++++++++++++++++++--
>>  2 files changed, 21 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/omap/crossbar.txt b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
>> index fb88585..6d2e2f5 100644
>> --- a/Documentation/devicetree/bindings/arm/omap/crossbar.txt
>> +++ b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
>> @@ -10,6 +10,7 @@ Required properties:
>>  - compatible : Should be "ti,irq-crossbar"
>>  - reg: Base address and the size of the crossbar registers.
>>  - ti,max-irqs: Total number of irqs available at the interrupt controller.
>> +- ti,max-crossbar-sources: Maximum number of crossbar sources that can be routed.
>>  - ti,reg-size: Size of a individual register in bytes. Every individual
>>  	    register is assumed to be of same size. Valid sizes are 1, 2, 4.
>>  - ti,irqs-reserved: List of the reserved irq lines that are not muxed using
>> @@ -22,6 +23,7 @@ Examples:
>>  			compatible = "ti,irq-crossbar";
>>  			reg = <0x4a002a48 0x130>;
>>  			ti,max-irqs = <160>;
>> +			ti,max-crossbar-sources = <400>;
>>  			ti,reg-size = <2>;
>>  			ti,irqs-reserved = <0 1 2 3 5 6 131 132 139 140>;
>>  		};
>> diff --git a/drivers/irqchip/irq-crossbar.c b/drivers/irqchip/irq-crossbar.c
>> index 2a73a66..cf69c4d 100644
>> --- a/drivers/irqchip/irq-crossbar.c
>> +++ b/drivers/irqchip/irq-crossbar.c
>> @@ -26,6 +26,7 @@
>>  /**
>>   * struct crossbar_device - crossbar device descriptio
>>   * @int_max: maximum number of supported interrupts
>> + * @max_crossbar_sources: Maximum number of crossbar sources
>>   * @irq_map: array of interrupts to crossbar number mapping
>>   * @crossbar_base: crossbar base address
>>   * @register_offsets: offsets for each irq number
>> @@ -33,6 +34,7 @@
>>   */
>>  struct crossbar_device {
>>  	uint int_max;
>> +	uint max_crossbar_sources;
>>  	uint *irq_map;
>>  	void __iomem *crossbar_base;
>>  	int *register_offsets;
>> @@ -126,12 +128,19 @@ static int crossbar_domain_xlate(struct irq_domain *d,
>>  				 unsigned int *out_type)
>>  {
>>  	int ret;
>> +	int req_num = intspec[1];
>>  
>> -	ret = get_prev_map_irq(intspec[1]);
>> +	if (req_num >= cb->max_crossbar_sources) {
>> +		pr_err("%s: requested crossbar number %d > max %d\n",
>> +		       __func__, req_num, cb->max_crossbar_sources);
>> +		return -EINVAL;
>> +	}
>> +
>> +	ret = get_prev_map_irq(req_num);
>>  	if (ret >= 0)
>>  		goto found;
>>  
>> -	ret = allocate_free_irq(intspec[1]);
>> +	ret = allocate_free_irq(req_num);
>>  
>>  	if (ret < 0)
>>  		return ret;
>> @@ -164,6 +173,14 @@ static int __init crossbar_of_init(struct device_node *node,
>>  	if (!cb->crossbar_base)
>>  		goto err_cb;
>>  
>> +	of_property_read_u32(node, "ti,max-crossbar-sources",
>> +			     &cb->max_crossbar_sources);
>> +	if (!cb->max_crossbar_sources) {
>> +		pr_err("missing 'ti,max-crossbar-sources' property\n");
>> +		ret = -EINVAL;
>> +		goto err_base;
>> +	}
> 
> This completely breaks all boards using old dtbs.  Please set
> max_crossbar_sources to a sane value (400) when the property is missing.
> 
>> +
>>  	of_property_read_u32(node, "ti,max-irqs", &max);
>>  	if (!max) {
>>  		pr_err("missing 'ti,max-irqs' property\n");
> 
> I know this is context, but you may want to look at this property as
> well and set it to a sane value instead of erroring out.
> 
 crossbar dts node itself is not there in any dts yet. So this is not applicable
 for any old boards. Any future dts with crossbar node should have this property
 defined.

Regards,
 Sricharan
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