1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2011-2017, The Linux Foundation
4 */
5
6#include <linux/errno.h>
7#include "slimbus.h"
8
9/**
10 * slim_ctrl_clk_pause() - Called by slimbus controller to enter/exit
11 *			   'clock pause'
12 * @ctrl: controller requesting bus to be paused or woken up
13 * @wakeup: Wakeup this controller from clock pause.
14 * @restart: Restart time value per spec used for clock pause. This value
15 *	isn't used when controller is to be woken up.
16 *
17 * Slimbus specification needs this sequence to turn-off clocks for the bus.
18 * The sequence involves sending 3 broadcast messages (reconfiguration
19 * sequence) to inform all devices on the bus.
20 * To exit clock-pause, controller typically wakes up active framer device.
21 * This API executes clock pause reconfiguration sequence if wakeup is false.
22 * If wakeup is true, controller's wakeup is called.
23 * For entering clock-pause, -EBUSY is returned if a message txn in pending.
24 */
25int slim_ctrl_clk_pause(struct slim_controller *ctrl, bool wakeup, u8 restart)
26{
27	int i, ret = 0;
28	unsigned long flags;
29	struct slim_sched *sched = &ctrl->sched;
30	struct slim_val_inf msg = {0, 0, NULL, NULL};
31
32	DEFINE_SLIM_BCAST_TXN(txn, SLIM_MSG_MC_BEGIN_RECONFIGURATION,
33				3, SLIM_LA_MANAGER, &msg);
34
35	if (wakeup == false && restart > SLIM_CLK_UNSPECIFIED)
36		return -EINVAL;
37
38	mutex_lock(&sched->m_reconf);
39	if (wakeup) {
40		if (sched->clk_state == SLIM_CLK_ACTIVE) {
41			mutex_unlock(&sched->m_reconf);
42			return 0;
43		}
44
45		/*
46		 * Fine-tune calculation based on clock gear,
47		 * message-bandwidth after bandwidth management
48		 */
49		ret = wait_for_completion_timeout(&sched->pause_comp,
50				msecs_to_jiffies(100));
51		if (!ret) {
52			mutex_unlock(&sched->m_reconf);
53			pr_err("Previous clock pause did not finish");
54			return -ETIMEDOUT;
55		}
56		ret = 0;
57
58		/*
59		 * Slimbus framework will call controller wakeup
60		 * Controller should make sure that it sets active framer
61		 * out of clock pause
62		 */
63		if (sched->clk_state == SLIM_CLK_PAUSED && ctrl->wakeup)
64			ret = ctrl->wakeup(ctrl);
65		if (!ret)
66			sched->clk_state = SLIM_CLK_ACTIVE;
67		mutex_unlock(&sched->m_reconf);
68
69		return ret;
70	}
71
72	/* already paused */
73	if (ctrl->sched.clk_state == SLIM_CLK_PAUSED) {
74		mutex_unlock(&sched->m_reconf);
75		return 0;
76	}
77
78	spin_lock_irqsave(&ctrl->txn_lock, flags);
79	for (i = 0; i < SLIM_MAX_TIDS; i++) {
80		/* Pending response for a message */
81		if (idr_find(&ctrl->tid_idr, i)) {
82			spin_unlock_irqrestore(&ctrl->txn_lock, flags);
83			mutex_unlock(&sched->m_reconf);
84			return -EBUSY;
85		}
86	}
87	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
88
89	sched->clk_state = SLIM_CLK_ENTERING_PAUSE;
90
91	/* clock pause sequence */
92	ret = slim_do_transfer(ctrl, &txn);
93	if (ret)
94		goto clk_pause_ret;
95
96	txn.mc = SLIM_MSG_MC_NEXT_PAUSE_CLOCK;
97	txn.rl = 4;
98	msg.num_bytes = 1;
99	msg.wbuf = &restart;
100	ret = slim_do_transfer(ctrl, &txn);
101	if (ret)
102		goto clk_pause_ret;
103
104	txn.mc = SLIM_MSG_MC_RECONFIGURE_NOW;
105	txn.rl = 3;
106	msg.num_bytes = 1;
107	msg.wbuf = NULL;
108	ret = slim_do_transfer(ctrl, &txn);
109
110clk_pause_ret:
111	if (ret) {
112		sched->clk_state = SLIM_CLK_ACTIVE;
113	} else {
114		sched->clk_state = SLIM_CLK_PAUSED;
115		complete(&sched->pause_comp);
116	}
117	mutex_unlock(&sched->m_reconf);
118
119	return ret;
120}
121EXPORT_SYMBOL_GPL(slim_ctrl_clk_pause);
122