From: Linus Walleij <linus.walleij@linaro.org>
To: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>
Subject: Re: [PATCH 3/3] gpio: mcp23s08: Add option to configure IRQ as active high
Date: Fri, 28 Nov 2014 16:39:31 +0100 [thread overview]
Message-ID: <CACRpkdasOLsPm2jGCLjLa=-mWSuu2GLQLaxbtr8TL6EeQhjPfg@mail.gmail.com> (raw)
In-Reply-To: <3020714.NCVpEFcdBT@ws-stein>
On Thu, Nov 27, 2014 at 3:36 PM, Alexander Stein
<alexander.stein@systec-electronic.com> wrote:
> On Thursday 27 November 2014 14:58:39, Linus Walleij wrote:
>> Sorry too confused by this, can you explain?
>
> Sure. Until now ODR is cleared as reset default while INTPOL explicitly gets cleared.
> So the INT output pin on the MCP23S17 is an active-low output pin which will trigger
> an active-low interrupt.
OK... I thought it was some kind of input line to the device. Now I get it, it
is what is generated *out* of this device. Please state this in the bindings.
> While this is useually great, as most interrupt pins are active low, our board design
> requires an active-high output.
OK I get it :)
> You might wonder why I then also changed IRQF_TRIGGER_LOW to
> IRQF_TRIGGER_HIGH for my board the interrupt line is actually active low.
> This is due the fact that GIC only supports active high-interrupts (any other flag
> results in request fail) but the microcontroller has a feature to inverse these interrupt triggers.
Very convoluted, but common in electronics, OK, no problem.
Yours,
Linus Walleij
next prev parent reply other threads:[~2014-11-28 15:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 8:38 [PATCH 1/3] gpio: mcp23s08: request a shared interrupt Alexander Stein
2014-11-17 8:38 ` [PATCH 2/3] gpio: mcp23s08: Add simple IRQ support for SPI devices Alexander Stein
2014-11-27 13:52 ` Linus Walleij
2014-11-17 8:38 ` [PATCH 3/3] gpio: mcp23s08: Add option to configure IRQ as active high Alexander Stein
2014-11-27 13:58 ` Linus Walleij
2014-11-27 14:36 ` Alexander Stein
2014-11-28 15:39 ` Linus Walleij [this message]
2014-11-27 13:51 ` [PATCH 1/3] gpio: mcp23s08: request a shared interrupt Linus Walleij
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