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authorSagar Dharia <sdharia@codeaurora.org>2017-12-12 02:43:01 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-12-19 13:01:03 +0300
commit4b14e62ad3c9e6e6774517f4077e197c0537fb07 (patch)
treec944a1253b54bee25c13fe0841bfdd4dd3bb641c /drivers/slimbus/sched.c
parentafbdcc7c384b0d446da08b1e0901dc176b41b9e0 (diff)
downloadlinux-4b14e62ad3c9e6e6774517f4077e197c0537fb07.tar.xz
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>
Diffstat (limited to 'drivers/slimbus/sched.c')
-rw-r--r--drivers/slimbus/sched.c121
1 files changed, 121 insertions, 0 deletions
diff --git a/drivers/slimbus/sched.c b/drivers/slimbus/sched.c
new file mode 100644
index 000000000000..af84997d2742
--- /dev/null
+++ b/drivers/slimbus/sched.c
@@ -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);