linux-kernel - Re: [PATCH] irq: fix the interrupt trigger type override issue

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Message-ID: <877cbu7596.ffs@tglx>
Date: Mon, 02 Sep 2024 11:51:33 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: richard clark <richard.xnu.clark@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 torvalds@...ux-foundation.org
Subject: Re: [PATCH] irq: fix the interrupt trigger type override issue

Richard!

On Mon, Sep 02 2024 at 16:42, richard clark wrote:
> On Mon, Sep 2, 2024 at 3:34 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>> 1) insmod()
>>      irq_create_fwspec_mapping(fwspec)
>>        irq_domain_translate(fwspec, ... &type); <- Sets type to the FW value
>>
>>        virq = irq_find_mapping(domain, hwirq);
>>        if (virq) {
>>          // Path not taken
>>        }
>>
>>        // Map interrupt
>>        ...
>>
>>        irqd_set_trigger_type(..., type);
>>
>> 2) rmmod()
>>      tears down mapping
>>
> This just tears down the action allocated and installed by
> request_irq(...), but does not teardown the irq's node inserted in the
> revmap_tree.

So what creates the mapping? If the driver creates it then why doesn't
it unmap it when it exits?

>> 3) insmod()
>>
>>       Should be exactly the same as #1 because the previous mapping was
>>       torn down by rmmod()
>>
> Not the same exactly, the {irq, irq_data} will still be in the
> revmap_tree, so it will enter another path in this case:

That's exactly the question. Why does the mapping persist?

>> So how exactly does that happen what you describe?
>>
> The logic is if the trigger type specified by request_irq(...) is not
> consistent with the firmware one, the request_irq will override the
> FW. We need to keep this logic the same as when we insmod the same
> kmod next time -- override the FW's too instead of returning a
> mismatch type error.

I can see how that can happen, but what's missing is the information why
this mapping persists and why it's tried to be set up again.

Thanks,

        tglx