linux-kernel - Re: [RFC PATCH 2/6] DRIVERS: IRQCHIP: CROSSBAR: Add support for Crossbar IP

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Message-ID: <5268F4C0.3060006@ti.com>
Date:	Thu, 24 Oct 2013 15:51:52 +0530
From:	Sricharan R <r.sricharan@...com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-doc@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linus.walleij@...aro.org>,
	<santosh.shilimkar@...com>, <linux@....linux.org.uk>,
	<tony@...mide.com>, <rnayak@...com>, <marc.zyngier@....com>,
	<grant.likely@...aro.org>, <rob.herring@...xeda.com>,
	<mark.rutland@....com>
Subject: Re: [RFC PATCH 2/6] DRIVERS: IRQCHIP: CROSSBAR: Add support for Crossbar
 IP

Hi Thomas,

On Thursday 24 October 2013 02:50 PM, Thomas Gleixner wrote:
> On Mon, 30 Sep 2013, Sricharan R wrote:
>> +/*
>> + * @int_max: maximum number of supported interrupts
>> + * @irq_map: array of interrupts to crossbar number mapping
>> + * @crossbar_base: crossbar base address
>> + * @register_offsets: offsets for each irq number
>> + */
>> +struct crossbar_device {
>> +	uint int_max;
>> +	uint *irq_map;
> Why do you need another map here?
>
> Isn't the linear_revmap of the irqdomain sufficient?
 linear_revmap gives the linux-irq for hw-irq,
 but here i need the crossbar number corresponding to
 the hwirq allocated. This is needed for setting up the
 crossbar register in map.
>> +static inline const u32 allocate_free_irq(int cb_no)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < cb->int_max; i++) {
>> +		if (cb->irq_map[i] == IRQ_FREE) {
>> +			cb->irq_map[i] = cb_no;
>> +			return i;
>> +		}
>> +	}
>> +
>> +	return -ENODEV;
>> +}
>> +
>> +static int crossbar_domain_xlate(struct irq_domain *d,
>> +				 struct device_node *controller,
>> +				 const u32 *intspec, unsigned int intsize,
>> +				 unsigned long *out_hwirq,
>> +				 unsigned int *out_type)
>> +{
>> +	return allocate_free_irq(intspec[1]) + GIC_IRQ_START;
> Mooo. In the error case you return:
>
>       -ENODEV + GIC_IRQ_START == -19 + 32 == 13
>
> Yikes.
 ya. will be a problem with error case. Will add a check here and
 in the gic as well to check for the return value.
>> +
>> +	/*
>> +	 * Register offsets are not linear because of the
>> +	 * reserved irqs. so find and store the offsets once.
>> +	 */
>> +	for (i = 0; i < max; i++) {
>> +		if (!cb->irq_map[i])
>> +			continue;
>> +
>> +		cb->register_offsets[i] = reserved;
>> +		reserved += size;
> I'm amazed by such a brilliant hardware design.
>
> Thanks,
>
> 	tglx

Regards,
 Sricharan
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