Initializing both CS on SPI1 causes data corruption

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1

Using two MCP23S17 I/O expanders via SPI1 with CS0 P9.28 and CS1 P9.42.
I am initializing each chip separately and doing a read immediately after, which produces the expected data. However, if I go back to read the first chip after initializing the second chip, the data is skewed and doesn’t read the first chip correctly. This happens even if I swap the order that the chips are initialized – whichever one was initialized first ends up with skewed data.

Software or kernel issue?

Here is my code and the output:
https://pastebin.com/L6qJGwPZ

2

Try again using the MCP23S17 bindings and the pinctrl-mcp23s08 driver:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pinctrl/pinctrl-mcp23s08.txt

Regards,

3

Sure, that name would be fine, but I would first start with this example:

https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-SPI0-MCP23S08-00A0.dts

Then change it to SPI1 and tweak the node to match the mcp23s17..

Regards,

4

Robert,

This caused my spidev1.0 and spidev1.1 to disappear.

Yes, that's good.. you can use the gpiolib/etc instead of hacking thru spidev..

Here's what I compiled:
/*
*
* 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/;
/plugin/;

#include <dt-bindings/board/am335x-bbw-bbb-base.h>
#include <dt-bindings/pinctrl/am33xx.h>

/ {
        compatible = "ti,beaglebone", "ti,beaglebone-black", "ti,beaglebone-green";

        /* identification */
        part-number = "BB-SPI1-MCP23S17";
        version = "00A0";

        /* state the resources this cape uses */
        exclusive-use =
                /* the pin header uses */
                "P9.31", /* spi1_sclk, SPI1_SCLK */
                "P9.29", /* spi1_d0, SPI1_MISO */
                "P9.30", /* spi1_d1, SPI1_MOSI */
                "P9.28", /* spi1_cs0, CS0 */
                "P9.42", /* spi1_cs1, CS1 */
                /* the hardware ip uses */
                "spi1";

        /*
         * Helper to show loaded overlays under: /proc/device-tree/chosen/overlays/
         */
        fragment@0 {
                target-path="/";
                __overlay__ {

                        chosen {
                                overlays {
                                        BB-SPI1-MCP23S17-00A0 = __TIMESTAMP__;
                                };
                        };
                };
        };

        /*
         * Free up the pins used by the cape from the pinmux helpers.
         */
        fragment@1 {
                target = <&ocp>;
                __overlay__ {
                        P9_28_pinmux { status = "disabled"; }; /* spi1_cs0 */
                        P9_30_pinmux { status = "disabled"; }; /* spi1_d1 */
                        P9_29_pinmux { status = "disabled"; }; /* spi1_d0 */
                        P9_31_pinmux { status = "disabled"; }; /* spi1_sclk */
                        P9_42_pinmux { status = "disabled"; }; /* spi1_cs1 */
                };
        };

        fragment@2 {
                target = <&am33xx_pinmux>;
                __overlay__ {
                        bb_spi0_pins: pinmux_bb_spi0_pins {

This label name doesn't match below... (aka: bb_spi1) replace ^ spi0
with spi1...

                                pinctrl-single,pins = <
                                        BONE_P9_31 (PIN_INPUT_PULLUP | MUX_MODE3) /* spi1_sclk.spi1_sclk */
                                        BONE_P9_29 (PIN_INPUT_PULLUP | MUX_MODE3) /* spi1_d0.spi1_d0 */
                                        BONE_P9_30 (PIN_OUTPUT_PULLUP | MUX_MODE3) /* spi1_d1.spi1_d1 */
                                        BONE_P9_28 (PIN_OUTPUT_PULLUP | MUX_MODE3) /* spi1_cs0.spi1_cs0 */
                                        BONE_P9_42 (PIN_OUTPUT_PULLUP | MUX_MODE2) /* spi1_cs1.spi1_cs1 */
                                >;
                        };
                };
        };

        fragment@3 {
                target = <&spi1>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;

                        status = "okay";
                        pinctrl-names = "default";
                        pinctrl-0 = <&bb_spi1_pins>;

                        gpiom1: gpio@0 {
                                compatible = "microchip,mcp23s17";
                                gpio-controller;
                                #gpio-cells = <2>;
                                microchip,spi-present-mask = <0x01>;
                                mcp,spi-present-mask = <0x01>;
                                spi-present-mask = <0x01>;
                                reg = <0>;
                                spi-max-frequency = <1000000>;
                        };

                        gpiom2: gpio@1 {
                                compatible = "microchip,mcp23s17";
                                gpio-conroller;

spelling: gpio-controller

                                #gpio-cells = <2>;
                                microchip,spi-present-mask = <0x01>;
                                mcp,spi-present-mask = <0x01>;
                                spi-present-mask = <0x01>;
                                reg = <1>;
                                spi-max-frequency = <1000000>;
                        };
                };
        };
};

Regards,