drivers/slimbus/sched.c

   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  */
  25 int 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
 110 clk_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 }
 121 EXPORT_SYMBOL_GPL(slim_ctrl_clk_pause);