Spidev cannot control chip select signal

Question

I use the kernel 3.12.rc4 on the embedded Linux device (olimex imx233 micro). My goal is to use /dev/spidev to communicate with another spi device.

I am editing arch/arm/boot/dts/imx23-olinuxino.dts as:

 ssp1: ssp@80034000 { #address-cells = <1>; #size-cells = <0>; compatible = "fsl,imx23-spi"; pinctrl-names = "default"; pinctrl-0 = <&spi2_pins_a>; clock-frequency = <1000000>; status = "okay"; spidev: spidev@0 { compatible = "spidev"; spi-max-frequency = <1000000>; reg = <1>; }; }; 

arch/arm/boot/dts/imx23.dtsi: has this configuration

 spi2_pins_a: spi2@0 { reg = <0>; fsl,pinmux-ids = < 0x0182 /* MX23_PAD_GPMI_WRN__SSP2_SCK */ 0x0142 /* MX23_PAD_GPMI_RDY1__SSP2_CMD */ 0x0002 /* MX23_PAD_GPMI_D00__SSP2_DATA0 */ 0x0032 /* MX23_PAD_GPMI_D03__SSP2_DATA3 */ >; fsl,drive-strength = <1>; fsl,voltage = <1>; fsl,pull-up = <1>; }; 

Pairing devices looks right. When I compile the kernel, I get /dev/spidev1.1 . After that, I use spidev_test.c and track contacts using an oscilloscope. The output signals of SCK and MOSI are correct, however, the chipselect is set to a logical height even during data transfer.

Is there a way to determine why spidev cannot set logic low during transmission? It seems that either additional things should be passed on to the kernel, or there is a problem with spidev that cannot control the chip selection. I wonder if I need to change something to spidev.h or spidev.c in the kernel / spi driver directory? or how can i solve it?

CPU Reference Guide

Answer 1

I have never used a device tree, but I'm still trying to help you.

The kernel creates the device /dev/spidev1.1 , so spidev connects to the SPI 1 bus, select chip 1. The start date of the chip selection starts at 0 , and you do not have another device connected to the SPI 1 bus.

As far as I know, reg = <1> tell the SPI kernel that spidev is connected to the choice of chip 1., but maybe your device is connected to the chip, select 0. So, reg = <0>