linux-imx

// SPDX-License-Identifier: GPL-2.0-only

/*

 * bios-less APM driver for ARM Linux

 *  Jamey Hicks <jamey@crl.dec.com>

 *  adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)

 *

 * APM 1.2 Reference:

 *   Intel Corporation, Microsoft Corporation. Advanced Power Management

 *   (APM) BIOS Interface Specification, Revision 1.2, February 1996.

 *

 * This document is available from Microsoft at:

 *    http://www.microsoft.com/whdc/archive/amp_12.mspx

 */

#include <linux/module.h>

#include <linux/poll.h>

#include <linux/slab.h>

#include <linux/mutex.h>

#include <linux/proc_fs.h>

#include <linux/seq_file.h>

#include <linux/miscdevice.h>

#include <linux/apm_bios.h>

#include <linux/capability.h>

#include <linux/sched.h>

#include <linux/suspend.h>

#include <linux/apm-emulation.h>

#include <linux/freezer.h>

#include <linux/device.h>

#include <linux/kernel.h>

#include <linux/list.h>

#include <linux/init.h>

#include <linux/completion.h>

#include <linux/kthread.h>

#include <linux/delay.h>

​

/*

 * One option can be changed at boot time as follows:

 *  apm=on/off          enable/disable APM

 */

​

/*

 * Maximum number of events stored

 */

#define APM_MAX_EVENTS      16

​

struct apm_queue {

    unsigned int        event_head;

    unsigned int        event_tail;

    apm_event_t     events[APM_MAX_EVENTS];

};

​

/*

 * thread states (for threads using a writable /dev/apm_bios fd):

 *

 * SUSPEND_NONE:    nothing happening

 * SUSPEND_PENDING: suspend event queued for thread and pending to be read

 * SUSPEND_READ:    suspend event read, pending acknowledgement

 * SUSPEND_ACKED:   acknowledgement received from thread (via ioctl),

 *          waiting for resume

 * SUSPEND_ACKTO:   acknowledgement timeout

 * SUSPEND_DONE:    thread had acked suspend and is now notified of

 *          resume

 *

 * SUSPEND_WAIT:    this thread invoked suspend and is waiting for resume

 *

 * A thread migrates in one of three paths:

 *  NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE

 *                  -6-> ACKTO -7-> NONE

 *  NONE -8-> WAIT -9-> NONE

 *

 * While in PENDING or READ, the thread is accounted for in the

 * suspend_acks_pending counter.

 *

 * The transitions are invoked as follows:

 *  1: suspend event is signalled from the core PM code

 *  2: the suspend event is read from the fd by the userspace thread

 *  3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)

 *  4: core PM code signals that we have resumed

 *  5: APM_IOC_SUSPEND ioctl returns

 *

 *  6: the notifier invoked from the core PM code timed out waiting

 *     for all relevant threds to enter ACKED state and puts those

 *     that haven't into ACKTO

 *  7: those threads issue APM_IOC_SUSPEND ioctl too late,

 *     get an error

 *

 *  8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),

 *     ioctl code invokes pm_suspend()

 *  9: pm_suspend() returns indicating resume

 */

enum apm_suspend_state {

    SUSPEND_NONE,

    SUSPEND_PENDING,