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

From: Daniel Palmer <daniel@0x0f.com>
To: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Cc: "Daniel Palmer" <daniel@thingy.jp>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	linux-mediatek@lists.infradead.org,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Marc Zyngier" <maz@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"YJ Chiang (江英杰)" <yj.chiang@mediatek.com>
Subject: Re: [PATCH v2] irqchip/irq-mst: Support polarity configuration
Date: Wed, 10 Mar 2021 19:20:27 +0900	[thread overview]
Message-ID: <CAFr9PX=dz1kt_BphpWr250asLiHFQNeBgNPhuPje==hzkcHWhg@mail.gmail.com> (raw)
In-Reply-To: <20210308143011.24538-1-mark-pk.tsai@mediatek.com>

Hi Mark-PK,

On Mon, 8 Mar 2021 at 23:30, Mark-PK Tsai <mark-pk.tsai@mediatek.com> wrote:
> From: Daniel Palmer <daniel@0x0f.com>
> >On Mon, 8 Mar 2021 at 15:05, Mark-PK Tsai <mark-pk.tsai@mediatek.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