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Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:37516) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1iX0Ge-0000UC-Bm; Tue, 19 Nov 2019 09:57:52 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1iX0Ga-0000ch-Hs; Tue, 19 Nov 2019 09:57:48 +0000 Date: Tue, 19 Nov 2019 09:57:48 +0000 From: Russell King - ARM Linux admin To: Marc Gonzalez Subject: Re: Using a GPIO as an interrupt line Message-ID: <20191119095748.GX25745@shell.armlinux.org.uk> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191119_015801_745549_06DAF93B X-CRM114-Status: GOOD ( 12.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marc Zyngier , GPIO , Linus Walleij , Linux ARM , MSM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Nov 19, 2019 at 10:28:15AM +0100, Marc Gonzalez wrote: > Hello, > > The board I'm working on provides a TCA9539 I/O expander. > Or, as the datasheet(*) calls it, a "Low Voltage 16-Bit I2C and > SMBus Low-Power I/O Expander with Interrupt Output, Reset Pin, > and Configuration Registers" > > (*) http://www.ti.com/lit/ds/symlink/tca9539.pdf > > The binding is documented in Documentation/devicetree/bindings/gpio/gpio-pca953x.txt > > I have some doubts about the interrupt output, described as: > > Optional properties: > - interrupts: interrupt specifier for the device's interrupt output. > > In my board's DT, the I/O expander is described as: > > exp1: gpio@74 { > compatible = "ti,tca9539"; > reg = <0x74>; > gpio-controller; > #gpio-cells = <2>; > reset-gpios = <&tlmm 96 GPIO_ACTIVE_LOW>; > pinctrl-names = "default"; > pinctrl-0 = <&top_exp_rst>; > interrupt-parent = <&tlmm>; > interrupts = <42 IRQ_TYPE_LEVEL_HIGH>; This specifies an interrupt signal, number 42, on the tlmm interrupt controller. It isn't a GPIO specification. Not every interrupt is a GPIO, and some SoCs can have dedicated interrupt pins that are exactly that. Hence, needlessly limiting an external device to requiring a GPIO for its interrupt is detrimental. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel