linux-kernel - Re: [PATCH v2] irqchip: xilinx: Add support for multiple instances

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Date:   Thu, 06 Feb 2020 09:15:54 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     Mubin Usman Sayyed <mubin.usman.sayyed@...inx.com>,
        tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        siva.durga.paladugu@...inx.com, anirudha.sarangi@...inx.com
Subject: Re: [PATCH v2] irqchip: xilinx: Add support for multiple instances

On 2020-02-06 09:11, Michal Simek wrote:
> On 06. 02. 20 10:09, Marc Zyngier wrote:
>> On 2020-02-06 07:06, Michal Simek wrote:
>>> On 05. 02. 20 17:53, Marc Zyngier wrote:
>>>> On 2020-02-05 14:05, Mubin Usman Sayyed wrote:
>> 
>> [...]
>> 
>>>>>  unsigned int xintc_get_irq(void)
>>>>>  {
>>>>> -       unsigned int hwirq, irq = -1;
>>>>> +       int hwirq, irq = -1;
>>>>> 
>>>>> -       hwirq = xintc_read(IVR);
>>>>> +       hwirq = xintc_read(primary_intc->base + IVR);
>>>>>         if (hwirq != -1U)
>>>>> -               irq = irq_find_mapping(xintc_irqc->root_domain, 
>>>>> hwirq);
>>>>> +               irq = irq_find_mapping(primary_intc->root_domain,
>>>>> hwirq);
>>>>> 
>>>>>         pr_debug("irq-xilinx: hwirq=%d, irq=%d\n", hwirq, irq);
>>>> 
>>>> I have the ugly feeling I'm reading the same code twice... Surely 
>>>> you
>>>> can
>>>> make these two functions common code.
>>> 
>>> I have some questions regarding this.
>>> I have updated one patchset which is adding support for Microblaze 
>>> SMP.
>>> And when I was looking at current wiring of this driver I have 
>>> decided
>>> to change it.
>>> 
>>> I have enabled  GENERIC_IRQ_MULTI_HANDLER and HANDLE_DOMAIN_IRQ.
>>> This driver calls set_handle_irq(xil_intc_handle_irq)
>>> and MB do_IRQ() call handle_arch_irq()
>>> and IRQ routine here is using handle_domain_irq().
>>> 
>>> I would expect that this chained IRQ handler can also use
>>> handle_domain_irq().
>>> 
>>> Is that correct understanding?
>> 
>> handle_domain_irq() implies that you have a set of pt_regs, 
>> representing
>> the context you interrupted. You can't fake that up, so I can't see 
>> how
>> you use it in a chained context.
> 
> ok. What's your recommendation for chained controller? Just go with
> irq_find_mapping?

For now, yes. I have (distant) plans to improve this.

         M.
-- 
Jazz is not dead. It just smells funny...