On 19/11/2019 10:57, Russell King - ARM Linux admin wrote: > On Tue, Nov 19, 2019 at 10:28:15AM +0100, Marc Gonzalez wrote: > >> 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>; As pointed out by ukleinek on IRC, I might have (??) specified the wrong trigger type. The data-sheet states: "The TCA9539 open-drain interrupt (INTn) output is activated when any input state differs from its corresponding Input Port register state, and is used to indicate to the system master that an input state has changed." (The data sheet speaks of "INT with a line on top"; what is the typical way to write that in ASCII? I was told that adding a trailing 'n' or 'b' was common.) According to that description, it looks like IRQ_TYPE_LEVEL_LOW? (Weird, because it worked well with 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. That makes complete sense. IIUC, what is missing in my DT spec is defining pin 42 as a GPIO pin. Looking more closely at top_exp_rst: top_exp_rst: top_exp_rst { mux { pins = "gpio96"; function = "gpio"; }; config { pins = "gpio96"; drive-strength = <2>; bias-pull-down; }; }; IIUC, this defines pin 96 as a GPIO pin (as well as defining some low-level properties of the pin). Likely I need something similar for pin 42? Regards.
