linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>

 */

#include <linux/kernel.h>

#include <linux/device.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <linux/sysfs.h>

​

#include "siox.h"

​

/*

 * The lowest bit in the SIOX status word signals if the in-device watchdog is

 * ok. If the bit is set, the device is functional.

 *

 * On writing the watchdog timer is reset when this bit toggles.

 */

#define SIOX_STATUS_WDG         0x01

​

/*

 * Bits 1 to 3 of the status word read as the bitwise negation of what was

 * clocked in before. The value clocked in is changed in each cycle and so

 * allows to detect transmit/receive problems.

 */

#define SIOX_STATUS_COUNTER     0x0e

​

/*

 * Each Siox-Device has a 4 bit type number that is neither 0 nor 15. This is

 * available in the upper nibble of the read status.

 *

 * On write these bits are DC.

 */

#define SIOX_STATUS_TYPE        0xf0

​

#define CREATE_TRACE_POINTS

#include <trace/events/siox.h>

​

static bool siox_is_registered;

​

static void siox_master_lock(struct siox_master *smaster)

{

    mutex_lock(&smaster->lock);

}

​

static void siox_master_unlock(struct siox_master *smaster)

{

    mutex_unlock(&smaster->lock);

}

​

static inline u8 siox_status_clean(u8 status_read, u8 status_written)

{

    /*

     * bits 3:1 of status sample the respective bit in the status

     * byte written in the previous cycle but inverted. So if you wrote the

     * status word as 0xa before (counter = 0b101), it is expected to get

     * back the counter bits as 0b010.

     *

     * So given the last status written this function toggles the there

     * unset counter bits in the read value such that the counter bits in

     * the return value are all zero iff the bits were read as expected to

     * simplify error detection.

     */