linux-kernel - Re: [PATCH] irqchip/loongson-liointc: Support to set IRQ_TYPE_EDGE

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Message-ID: <CAAhV-H6r_iiKauPB=7eWhyTetvsTvxt5O9HtmmKb72y62yvXnA@mail.gmail.com>
Date: Sun, 6 Apr 2025 20:46:12 +0800
From: Huacai Chen <chenhuacai@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Huacai Chen <chenhuacai@...ngson.cn>, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>, 
	Jiaxun Yang <jiaxun.yang@...goat.com>, stable@...r.kernel.org, 
	Yinbo Zhu <zhuyinbo@...ngson.cn>
Subject: Re: [PATCH] irqchip/loongson-liointc: Support to set IRQ_TYPE_EDGE_BOTH

On Sun, Apr 6, 2025 at 6:18 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Sun, Apr 06 2025 at 17:46, Huacai Chen wrote:
> > On Thu, Apr 3, 2025 at 11:48 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> >> But it won't trigger on both. So no, you cannot claim that this fixes
> >> anything.
> > Yes, it won't trigger on both (not perfect), but it allows drivers
> > that request "both" work (better than fail to request), and there are
>
> By some definition of 'work'. There is probably a good technical reason
> why those drivers expect EDGE_BOTH to work correctly and otherwise fail
> to load.
The real problem we encounter is the MMC driver. In
drivers/mmc/core/slot-gpio.c there is
devm_request_threaded_irq(host->parent, irq,
                        NULL, ctx->cd_gpio_isr,
                        IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
IRQF_ONESHOT,
                        ctx->cd_label, host);

"IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING" is an alias of
"IRQ_TYPE_EDGE_RISING | IRQ_TYPE_EDGE_FALLING", and
"IRQ_TYPE_EDGE_RISING | IRQ_TYPE_EDGE_FALLING" is
"IRQ_TYPE_EDGE_BOTH".

Except MMC, "grep IRQ_TYPE_EDGE_BOTH drivers" can give some more examples.

Huacai

>
> You completely fail to explain, why this hack actually 'works' and what
> the implications are for such drivers.
>
> > other irqchip drivers that do similar things.
>
> Justifying bogosity with already existing bogosity is not a technical
> argument.
>
> Thanks,
>
>         tglx