linux-kernel - Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse mapping

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Date:	Fri, 27 Nov 2015 11:46:38 +0000
From:	Qais Yousef <qais.yousef@...tec.com>
To:	<linux-kernel@...r.kernel.org>
CC:	<tglx@...utronix.de>, <jason@...edaemon.net>,
	<marc.zyngier@....com>, <jiang.liu@...ux.intel.com>,
	<ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>
Subject: Re: [PATCH v2 09/19] genirq: Add a new function to get IPI reverse
 mapping

On 11/25/2015 12:06 PM, Qais Yousef wrote:
> +
> +/**
> + * ipi_get_hwirq - get the hwirq associated with an IPI to a cpu
> + * @irq: linux irq number
> + * @cpu: the cpu to find the revmap for
> + *
> + * When dealing with coprocessors IPI, we need to inform it of the hwirq it
> + * needs to use to receive and send IPIs. This function provides the revmap
> + * to get this info to pass on to coprocessor firmware.
> + *
> + * Returns hwirq value on success and INVALID_HWIRQ on failure.
> + */
> +irq_hw_number_t ipi_get_hwirq(unsigned int irq, unsigned int cpu)
> +{
> +	struct irq_data *data = irq_get_irq_data(irq);
> +	struct ipi_mask *ipimask = data ? irq_data_get_ipi_mask(data) : NULL;
> +	irq_hw_number_t hwirq;
> +
> +	if (!data || !ipimask)
> +		return INVALID_HWIRQ;
> +
> +	if (cpu > ipimask->nbits)
> +		return INVALID_HWIRQ;
> +
> +	if (!test_bit(cpu, ipimask->cpu_bitmap))
> +		return INVALID_HWIRQ;
> +
> +	if (irq_domain_is_ipi_per_cpu(data->domain)) {
> +		data = irq_get_irq_data(irq + cpu - ipimask->offset);
> +		hwirq = data ? irqd_to_hwirq(data) : INVALID_HWIRQ;
> +	} else {
> +		hwirq = irqd_to_hwirq(data) + cpu - ipimask->offset;
> +	}
> +
> +	return hwirq;
> +}
> +EXPORT_SYMBOL_GPL(ipi_get_hwirq);


While trying to get my remoteproc driver work with this I uncovered a 
problem with this approach.

mips-gic doesn't store the actual hwirq in the irq_data. It uses 
GIC_SHARED_TO_HWIRQ() and GIC_HWIRQ_TO_SHARED() to add and remove an offset.

I'll add a new chip function irq_get_raw_hwirq(struct irq_data *d) that 
will return the real hardware value of hwirq. If not defined, I'll 
revert back to using the irqd_to_hwirq().

Objections?

Thanks,
Qais
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