Re: [PATCH 04/13] irqchip: Add driver for Loongson-3 I/O interrupt controller

From: Marc Zyngier
Date: Wed Aug 28 2019 - 12:02:23 EST

On 28/08/2019 16:31, Jiaxun Yang wrote:
> On 2019/8/28 äå2:59, Marc Zyngier wrote:
>> On Wed, 28 Aug 2019 08:27:05 +0800
>> Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote:
>>> On 2019/8/28 äå12:45, Marc Zyngier wrote:
>>>> On 27/08/2019 09:52, Jiaxun Yang wrote:
>>>>> + chained_irq_enter(chip, desc);
>>>>> +
>>>>> + pending = readl(priv->intc_base + LS3_REG_INTC_EN_STATUS) &
>>>>> + readl(priv->intc_base + LS3_REG_INTC_STATUS);
>>>> Reading the enabled status from the HW on each interrupt? I'm sure
>>>> that's pretty cheap...
>>> Seems expensive but to deal with a buggy hardware... That's worthy.
>> How broken is it? You very much seem to rely on the HW being correct
>> here, since you trust it exclusively. I'd expect the enable mask to be
>> a SW construct if you didn't blindly trust it
> Hi Marc
> Thanks for your answering.
> The vendor code did this and said there is a HW issue. I just don't have
> the guts to remove this check.
> Seems like sometimes masked interrupt may get ISR set wrongly.

And that would just as well avoided by a SW managed mask.

>> And if this is truly the right way to do it, please document the
>> various problems with the controller so that we don't break it at a
>> later time.
> Thanks, will do.
>> Then how comes this comes from the irqchip's DT node? This should be
>> part of the endpoint's interrupt specifier.
> In theory it should be, However if we set different interrupt
> lines/cores on that controller, interrupts may get lost. It means we can
> only have single parent core/interrupt.
> So I'd prefer just set them uniformly by controller's dt-binding to
> prevent confusing.

And I disagree. You can document the restriction, and even maybe enforce
it by validating the DT one way or another. But we're not putting what
ends up being a routing table in the irqchip binding.

Jazz is not dead, it just smells funny...