linux-kernel - Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain

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Date:	Mon, 16 Nov 2015 18:24:03 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Qais Yousef <qais.yousef@...tec.com>
cc:	linux-kernel@...r.kernel.org, jason@...edaemon.net,
	marc.zyngier@....com, jiang.liu@...ux.intel.com,
	ralf@...ux-mips.org, linux-mips@...ux-mips.org
Subject: Re: [PATCH 10/14] irqchip/mips-gic: Add a IPI hierarchy domain

On Thu, 12 Nov 2015, Qais Yousef wrote:
> Issues I'm seeing:
> 
>     - Device domain would be identical to GIC domain and it would defer
> everything to the parent domain except for the extra level of indirection. No?
 
It's not identical. It's a subset of the GIC domain and it has
different semantics than the IPI domain.

>     - The race condition I mentioned in my earlier email where we must be told
> what hwirqs are available because we can't guarantee there's no real device
> connected to it which could interfere with the operation. We have always to
> work on a pre reserved set defined by the system. Currently GIC hard codes
> this set, but I'll be making it a DT property in the future.

We do that better now as we really don't want to start over when it
turns out that the DT property imposes other issues on it.
 
>     - If we remove the mapping, how can a coprocessor drivers find out the
> reverse mapping to pass the hwirq to the firmware so that it can send and
> listen on the correct hwirqs? I have to say my current patches missed dealing
> with this problem. Now I have something to test my rproc driver on I came to
> realise I haven't added the function to do the reverse mapping.

int ipi_get_hw_irq(int irq)
{
	struct irq_data *d = irq_get_irq_data(irq);
	return d ? irqd_to_hwirq(d);
}
 
Hmm?

Thanks,

	tglx
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