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

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Message-ID: <575c6350-139b-65b9-f9e2-2633656baa85@xilinx.com>
Date:   Thu, 6 Feb 2020 10:11:27 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Marc Zyngier <maz@...nel.org>,
        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 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?

> 
> [...]
> 
>>>> +       intc_dev->name = intc->full_name;
>>>
>>> No. The world doesn't need to see the OF path of your interrupt
>>> controller in /proc/cpuinfo.
>>> The name that was there before was perfectly descriptive, please stick
>>> to it.
>>
>> It should be showing name like interrupt-controller@...00000.
>> Do you think that we really should stick with just fixed name?
>> There could be multiple instances in the system and you will have no
>> idea how they are connected.
> 
> What is that used for? Debugging. We have a whole infrastructure for that
> (GENERIC_IRQ_DEBUGFS), which is the right tool for the job. If it needs
> improvement, please let me know what is missing.

Let me take a look.

> Also, anything in /proc is ABI, so we don't change it randomly.

ok.

Thanks,
Michal