// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2011-2017, The Linux Foundation
 */

#include <linux/errno.h>
#include "slimbus.h"

/**
 * slim_ctrl_clk_pause() - Called by slimbus controller to enter/exit
 *                         'clock pause'
 * @ctrl: controller requesting bus to be paused or woken up
 * @wakeup: Wakeup this controller from clock pause.
 * @restart: Restart time value per spec used for clock pause. This value
 *      isn't used when controller is to be woken up.
 *
 * Slimbus specification needs this sequence to turn-off clocks for the bus.
 * The sequence involves sending 3 broadcast messages (reconfiguration
 * sequence) to inform all devices on the bus.
 * To exit clock-pause, controller typically wakes up active framer device.
 * This API executes clock pause reconfiguration sequence if wakeup is false.
 * If wakeup is true, controller's wakeup is called.
 * For entering clock-pause, -EBUSY is returned if a message txn in pending.
 */
int slim_ctrl_clk_pause(struct slim_controller *ctrl, bool wakeup, u8 restart)
{
        int i, ret = 0;
        unsigned long flags;
        struct slim_sched *sched = &ctrl->sched;
        struct slim_val_inf msg = {0, 0, NULL, NULL};

        DEFINE_SLIM_BCAST_TXN(txn, SLIM_MSG_MC_BEGIN_RECONFIGURATION,
                                3, SLIM_LA_MANAGER, &msg);

        if (wakeup == false && restart > SLIM_CLK_UNSPECIFIED)
                return -EINVAL;

        mutex_lock(&sched->m_reconf);
        if (wakeup) {
                if (sched->clk_state == SLIM_CLK_ACTIVE) {
                        mutex_unlock(&sched->m_reconf);
                        return 0;
                }

                /*
                 * Fine-tune calculation based on clock gear,
                 * message-bandwidth after bandwidth management
                 */
                ret = wait_for_completion_timeout(&sched->pause_comp,
                                msecs_to_jiffies(100));
                if (!ret) {
                        mutex_unlock(&sched->m_reconf);
                        pr_err("Previous clock pause did not finish");
                        return -ETIMEDOUT;
                }
                ret = 0;

                /*
                 * Slimbus framework will call controller wakeup
                 * Controller should make sure that it sets active framer
                 * out of clock pause
                 */
                if (sched->clk_state == SLIM_CLK_PAUSED && ctrl->wakeup)
                        ret = ctrl->wakeup(ctrl);
                if (!ret)
                        sched->clk_state = SLIM_CLK_ACTIVE;
                mutex_unlock(&sched->m_reconf);

                return ret;
        }

        /* already paused */
        if (ctrl->sched.clk_state == SLIM_CLK_PAUSED) {
                mutex_unlock(&sched->m_reconf);
                return 0;
        }

        spin_lock_irqsave(&ctrl->txn_lock, flags);
        for (i = 0; i < SLIM_MAX_TIDS; i++) {
                /* Pending response for a message */
                if (idr_find(&ctrl->tid_idr, i)) {
                        spin_unlock_irqrestore(&ctrl->txn_lock, flags);
                        mutex_unlock(&sched->m_reconf);
                        return -EBUSY;
                }
        }
        spin_unlock_irqrestore(&ctrl->txn_lock, flags);

        sched->clk_state = SLIM_CLK_ENTERING_PAUSE;

        /* clock pause sequence */
        ret = slim_do_transfer(ctrl, &txn);
        if (ret)
                goto clk_pause_ret;

        txn.mc = SLIM_MSG_MC_NEXT_PAUSE_CLOCK;
        txn.rl = 4;
        msg.num_bytes = 1;
        msg.wbuf = &restart;
        ret = slim_do_transfer(ctrl, &txn);
        if (ret)
                goto clk_pause_ret;

        txn.mc = SLIM_MSG_MC_RECONFIGURE_NOW;
        txn.rl = 3;
        msg.num_bytes = 1;
        msg.wbuf = NULL;
        ret = slim_do_transfer(ctrl, &txn);

clk_pause_ret:
        if (ret) {
                sched->clk_state = SLIM_CLK_ACTIVE;
        } else {
                sched->clk_state = SLIM_CLK_PAUSED;
                complete(&sched->pause_comp);
        }
        mutex_unlock(&sched->m_reconf);

        return ret;
}
EXPORT_SYMBOL_GPL(slim_ctrl_clk_pause);