linux-kernel - Re: [PATCH v2] irqchip/irq-mst: Support polarity configuration

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Date:   Wed, 10 Mar 2021 19:20:27 +0900
From:   Daniel Palmer <daniel@...f.com>
To:     Mark-PK Tsai <mark-pk.tsai@...iatek.com>
Cc:     Daniel Palmer <daniel@...ngy.jp>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mediatek@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        YJ Chiang (江英杰) <yj.chiang@...iatek.com>
Subject: Re: [PATCH v2] irqchip/irq-mst: Support polarity configuration

Hi Mark-PK,

On Mon, 8 Mar 2021 at 23:30, Mark-PK Tsai <mark-pk.tsai@...iatek.com> wrote:
> From: Daniel Palmer <daniel@...f.com>
> >On Mon, 8 Mar 2021 at 15:05, Mark-PK Tsai <mark-pk.tsai@...iatek.com> wrote:
> >> +static int mst_irq_chip_set_type(struct irq_data *data, unsigned int type)
> >       > +{
> >> +       if (type != IRQ_TYPE_LEVEL_LOW && type != IRQ_TYPE_LEVEL_HIGH)
> >> +               return -EINVAL;
> >> +
> >
> >Does this mean we can't do rising or falling edge interrupts?
>
> Yes, the interrupt of mst-intc is either level high or level low.
> Actually the input signal can be pulse, but it will be converted to level
> by the latch in mst-intc.

Are the GPIO connected interrupts meant to be configured as level
interrupts then?
For the MStar MSC313(e) there are 4 (that I know of) GPIO lines that
are wired into the mst-intc that requires EOI.
Until this patch with those lines configured as a rising edge a single
interrupt came each time the GPIO was pulled up as far as I remember.

I'm probably misunderstanding but a level interrupt doesn't seem to
make sense for a GPIO as it can't be serviced to clear the interrupt.

Thanks,

Daniel