Linux/PROCESSOR-SDK-AM335X: Cannot use mcp23s17 kernel driver with Beaglebone black

Hello Pavel,

thank you for your message. For being more clear, let's consider the two cases: 1) mcp23s17 controlled by my own library and 2) mcp23s17 controlled by kernel driver.

1. mcp23s17 controlled by my own library
   

   Before writing to the forum, regarding the pins direction, I've made several tests.
   In particular if the PINS are set as follow :

                    0x150 0x10 /* spi0_sclk, OUTPUT_PULLUP | MODE0 */

                    0x154 0x10 /* spi0_d0, OUTPUT_PULLUP | MODE0 */

                    0x158 0x30 /* spi0_d1, INPUT_PULLUP | MODE0 */

                    0x15c 0x10 /* spi0_cs0, OUTPUT_PULLUP | MODE0 */

   as they should be in an SPI master or even:

            0x150 0x30 /* spi0_sclk, INPUT_PULLUP | MODE0 */  

            0x154 0x30 /* spi0_d0, INPUT_PULLUP | MODE0 */  

            0x158 0x10 /* spi0_d1, OUTPUT_PULLUP | MODE0 */  

            0x15c 0x10 /* spi0_cs0, OUTPUT_PULLUP | MODE0 */

   as described in the following links:

   -

   I can write correctly but I cannot read from the peripheral. The only solution that worked both for writing and reading correctly, was to set all the pins as INPUT_PULL_UP. Besides it was important to set SPI in mode 0 "Low at idle, capture on rising clock edge".

2. mcp23s17 controlled by kernel driver
   
   I've tried the modifications that you indicated me, as you can see in the modified device tree in attachment
   custom_board2.txt

   /*
    * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
    *
    * This program is free software; you can redistribute it and/or modify
    * it under the terms of the GNU General Public License version 2 as
    * published by the Free Software Foundation.
    */
   /dts-v1/;
   
   #include "am33xx.dtsi"
   #include "am335x-bone-common.dtsi"
   
   &ldo3_reg {
       regulator-min-microvolt = <1800000>;
       regulator-max-microvolt = <1800000>;
       regulator-always-on;
   };
   
   &sgx {
       status = "okay";
   };
   
   / {
   	model = "TI AM335x BeagleBone Black";
   	compatible = "ti,am335x-bone-black", "ti,am335x-bone", "ti,am33xx";
   };
   
   &cpu0_opp_table {
   	/*
   	 * All PG 2.0 silicon may not support 1GHz but some of the early
   	 * BeagleBone Blacks have PG 2.0 silicon which is guaranteed
   	 * to support 1GHz OPP so enable it for PG 2.0 on this board.
   	 */
   	oppnitro-1000000000 {
   		opp-supported-hw = <0x06 0x0100>;
   	};
   };
   
   &tscadc {
           adc {
                   ti,adc-channels = <4 5 6 7>;
   		status = "okay";
           };
   };
   
   &mmc1 {
       vmmc-supply = <&vmmcsd_fixed>;
   };
   
   &rtc {
   	system-power-controller;
   };
   
   
   /* Common pinmux */
   &am33xx_pinmux {
   
       ecap0_pins: pwm_pins {
   		pinctrl-single,pins = <
   			0x164 0x0	/* eCAP0_in_PWM0_out.eCAP0_in_PWM0_out MODE0 */
   		>;
   	};
       
       spi0_pins: pinmux_spi0_pins {
               pinctrl-single,pins = <
                   0x150 (PIN_OUTPUT_PULLUP | MUX_MODE0)   /* spi0_sclk.spi0_sclk, OUTPUT_PULLUP | MODE0 */
                   0x154 (PIN_OUTPUT_PULLUP | MUX_MODE0)   /* spi0_d0.spi0_d0, INPUT_PULLUP | MODE0 0x30 */
                   0x158 (PIN_INPUT_PULLUP | MUX_MODE0)  /* spi0_d1.spi0_d1, OUTPUT_PULLUP | MODE0 */
                   0x15c (PIN_OUTPUT_PULLUP | MUX_MODE0)   /* spi0_cs0.spi0_cs0, OUTPUT_PULLUP | MODE0 0x10 */
               >;
           };
   };
   
   /* PWM */
   &epwmss0 {
           status = "okay";
   
           ecap0: ecap@48300100 {
                   status = "okay";
                   pinctrl-names = "default";
                   pinctrl-0 = <&ecap0_pins>;
           };
   };
   
   // mcp23s17
   &spi0 {
           status = "okay";
           pinctrl-names = "default";
           pinctrl-0 = <&spi0_pins>;
   	ti,pindir-d0-out-d1-in = <1>;
           gpiom0:gpiom0@0{
               compatible = "microchip,mcp23s17";
               spi-cpha=<0>;
               spi-cpol=<0>;
               gpio-controller;
               #gpio-cells = <2>;
               spi-present-mask = <0X01>;		// Periferiche connesse considerando A1,A2,A3 
               reg = <0>;                          // specify the chip select line MCP23017
               spi-max-frequency = <1000000>;
           };
   };
   
   // Generic device
   /*&spi0{
   	pinctrl-names = "default";
   	pinctrl-0 = <&spi0_pins>;
   	status = "okay";
   	ti,pindir-d0-out-d1-in = <1>;
   
   	spidev@0{
   		pinctrl-0 = <&spi0_pins>;		
   		compatible = "linux,spidev";
   		reg = <0>;
   		spi-max-frequency = <10000000>;
   	};
   };*/
   

   , but unfortunately the result is the same. I've also tried to se the SPI MODE with spi-cpha=<0>; spi-cpol=<0>; but unsuccesfully.

Have you got the possibility to try it ?

Thank you.