linux-imx

/*

 * gpio-max3191x.c - GPIO driver for Maxim MAX3191x industrial serializer

 *

 * Copyright (C) 2017 KUNBUS GmbH

 *

 * The MAX3191x makes 8 digital 24V inputs available via SPI.

 * Multiple chips can be daisy-chained, the spec does not impose

 * a limit on the number of chips and neither does this driver.

 *

 * Either of two modes is selectable: In 8-bit mode, only the state

 * of the inputs is clocked out to achieve high readout speeds;

 * In 16-bit mode, an additional status byte is clocked out with

 * a CRC and indicator bits for undervoltage and overtemperature.

 * The driver returns an error instead of potentially bogus data

 * if any of these fault conditions occur.  However it does allow

 * readout of non-faulting chips in the same daisy-chain.

 *

 * MAX3191x supports four debounce settings and the driver is

 * capable of configuring these differently for each chip in the

 * daisy-chain.

 *

 * If the chips are hardwired to 8-bit mode ("modesel" pulled high),

 * gpio-pisosr.c can be used alternatively to this driver.

 *

 * https://datasheets.maximintegrated.com/en/ds/MAX31910.pdf

 * https://datasheets.maximintegrated.com/en/ds/MAX31911.pdf

 * https://datasheets.maximintegrated.com/en/ds/MAX31912.pdf

 * https://datasheets.maximintegrated.com/en/ds/MAX31913.pdf

 * https://datasheets.maximintegrated.com/en/ds/MAX31953-MAX31963.pdf

 *

 * 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.

 */

​

#include <linux/bitmap.h>

#include <linux/crc8.h>

#include <linux/gpio/consumer.h>

#include <linux/gpio/driver.h>

#include <linux/module.h>

#include <linux/spi/spi.h>

​

enum max3191x_mode {

    STATUS_BYTE_ENABLED,

    STATUS_BYTE_DISABLED,

};

​

/**

 * struct max3191x_chip - max3191x daisy-chain

 * @gpio: GPIO controller struct

 * @lock: protects read sequences

 * @nchips: number of chips in the daisy-chain

 * @mode: current mode, 0 for 16-bit, 1 for 8-bit;

 *  for simplicity, all chips in the daisy-chain are assumed

 *  to use the same mode

 * @modesel_pins: GPIO pins to configure modesel of each chip

 * @fault_pins: GPIO pins to detect fault of each chip

 * @db0_pins: GPIO pins to configure debounce of each chip

 * @db1_pins: GPIO pins to configure debounce of each chip

 * @mesg: SPI message to perform a readout

 * @xfer: SPI transfer used by @mesg

 * @crc_error: bitmap signaling CRC error for each chip

 * @overtemp: bitmap signaling overtemperature alarm for each chip

 * @undervolt1: bitmap signaling undervoltage alarm for each chip

 * @undervolt2: bitmap signaling undervoltage warning for each chip

 * @fault: bitmap signaling assertion of @fault_pins for each chip

 * @ignore_uv: whether to ignore undervoltage alarms;

 *  set by a device property if the chips are powered through

 *  5VOUT instead of VCC24V, in which case they will constantly

 *  signal undervoltage;

 *  for simplicity, all chips in the daisy-chain are assumed

 *  to be powered the same way

 */

struct max3191x_chip {

    struct gpio_chip gpio;

    struct mutex lock;

    u32 nchips;

    enum max3191x_mode mode;

    struct gpio_descs *modesel_pins;

    struct gpio_descs *fault_pins;

    struct gpio_descs *db0_pins;

    struct gpio_descs *db1_pins;

    struct spi_message mesg;

    struct spi_transfer xfer;

    unsigned long *crc_error;

    unsigned long *overtemp;

    unsigned long *undervolt1;

    unsigned long *undervolt2;

    unsigned long *fault;

    bool ignore_uv;

};

​