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