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slimbus: Add support for 'clock-pause' feature
Per SLIMbus specification, a reconfiguration sequence known as 'clock pause' needs to be broadcast over the bus while entering low- power mode. Clock-pause is initiated by the controller driver. To exit clock-pause, controller typically wakes up the framer device. Since wakeup precedure is controller-specific, framework calls it via controller's function pointer to invoke it. Signed-off-by: Sagar Dharia <sdharia@codeaurora.org> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Reviwed-by: Mark Brown <broonie@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Sagar Dharia
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Greg Kroah-Hartman
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Dec 19, 2017
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,121 @@ | ||
| // 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); |
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