[PATCH V4 5/6] slimbus: Add support for 'clock-pause' feature

From: Sagar Dharia
Date: Sat Feb 06 2016 - 13:46:04 EST

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@xxxxxxxxxxxxxx>
---
drivers/slimbus/Makefile | 2 +-
drivers/slimbus/slim-core.c | 13 +++++
drivers/slimbus/slim-messaging.c | 50 ++++++++++++++--
drivers/slimbus/slim-sched.c | 122 +++++++++++++++++++++++++++++++++++++++
include/linux/slimbus.h | 69 +++++++++++++++++++++-
5 files changed, 248 insertions(+), 8 deletions(-)
create mode 100644 drivers/slimbus/slim-sched.c

diff --git a/drivers/slimbus/Makefile b/drivers/slimbus/Makefile
index 574a892..cc0d20a 100644
--- a/drivers/slimbus/Makefile
+++ b/drivers/slimbus/Makefile
@@ -1,5 +1,5 @@
#
# Makefile for kernel slimbus framework.
#
-obj-$(CONFIG_SLIMBUS) += slim-core.o slim-messaging.o
+obj-$(CONFIG_SLIMBUS) += slim-core.o slim-messaging.o slim-sched.o
obj-$(CONFIG_SLIM_QCOM_CTRL) += slim-qcom-ctrl.o
diff --git a/drivers/slimbus/slim-core.c b/drivers/slimbus/slim-core.c
index 27c7dec..5d67e53 100644
--- a/drivers/slimbus/slim-core.c
+++ b/drivers/slimbus/slim-core.c
@@ -443,6 +443,8 @@ int slim_register_controller(struct slim_controller *ctrl)
mutex_init(&ctrl->m_ctrl);
spin_lock_init(&ctrl->tx.lock);
spin_lock_init(&ctrl->rx.lock);
+ mutex_init(&ctrl->sched.m_reconf);
+ init_completion(&ctrl->sched.pause_comp);

ctrl->pending_wr = kcalloc((ctrl->tx.n - 1),
sizeof(struct slim_pending),
@@ -715,6 +717,14 @@ int slim_assign_laddr(struct slim_controller *ctrl, struct slim_eaddr *e_addr,
struct slim_device *slim;
struct slim_addrt *temp;

+ ret = pm_runtime_get_sync(ctrl->dev.parent);
+
+ if (ctrl->sched.clk_state != SLIM_CLK_ACTIVE) {
+ dev_err(&ctrl->dev, "slim ctrl not active,state:%d, ret:%d\n",
+ ctrl->sched.clk_state, ret);
+ goto slimbus_not_active;
+ }
+
mutex_lock(&ctrl->m_ctrl);
/* already assigned */
if (ctrl_getaddr_entry(ctrl, e_addr, &i) == 0) {
@@ -783,6 +793,9 @@ ret_assigned_laddr:
}
mutex_unlock(&slim->report_lock);
}
+slimbus_not_active:
+ pm_runtime_mark_last_busy(ctrl->dev.parent);
+ pm_runtime_put_autosuspend(ctrl->dev.parent);
return ret;
}
EXPORT_SYMBOL_GPL(slim_assign_laddr);
diff --git a/drivers/slimbus/slim-messaging.c b/drivers/slimbus/slim-messaging.c
index 3785c35..91d39d6 100644
--- a/drivers/slimbus/slim-messaging.c
+++ b/drivers/slimbus/slim-messaging.c
@@ -10,6 +10,7 @@
* GNU General Public License for more details.
*/
#include <linux/slab.h>
+#include <linux/pm_runtime.h>
#include <linux/slimbus.h>

/**
@@ -42,6 +43,9 @@ void slim_msg_response(struct slim_controller *ctrl, u8 *reply, u8 tid, u8 len)
if (msg->comp_cb)
msg->comp_cb(msg->ctx, 0);
spin_unlock_irqrestore(&ctrl->txn_lock, flags);
+ /* Remove runtime-pm vote now that response was received for TID txn */
+ pm_runtime_mark_last_busy(ctrl->dev.parent);
+ pm_runtime_put_autosuspend(ctrl->dev.parent);
}
EXPORT_SYMBOL_GPL(slim_msg_response);

@@ -64,11 +68,21 @@ int slim_processtxn(struct slim_controller *ctrl,
int ret, i = 0;
unsigned long flags;
u8 *buf;
- bool async = false;
+ bool async = false, clk_pause_msg = false;
struct slim_cb_data cbd;
DECLARE_COMPLETION_ONSTACK(done);
bool need_tid = slim_tid_txn(txn->mt, txn->mc);

+ /*
+ * do not vote for runtime-PM if the transactions are part of clock
+ * pause sequence
+ */
+ if (ctrl->sched.clk_state == SLIM_CLK_ENTERING_PAUSE &&
+ (txn->mt == SLIM_MSG_MT_CORE &&
+ txn->mc >= SLIM_MSG_MC_BEGIN_RECONFIGURATION &&
+ txn->mc <= SLIM_MSG_MC_RECONFIGURE_NOW))
+ clk_pause_msg = true;
+
if (!txn->msg->comp_cb) {
txn->msg->comp_cb = slim_sync_default_cb;
cbd.comp = &done;
@@ -77,7 +91,7 @@ int slim_processtxn(struct slim_controller *ctrl,
async = true;
}

- buf = slim_get_tx(ctrl, txn, need_tid);
+ buf = slim_get_tx(ctrl, txn, need_tid, clk_pause_msg);
if (!buf)
return -ENOMEM;

@@ -91,7 +105,8 @@ int slim_processtxn(struct slim_controller *ctrl,
if (ctrl->last_tid == (SLIM_MAX_TIDS - 1)) {
spin_unlock_irqrestore(&ctrl->txn_lock, flags);
slim_return_tx(ctrl, -ENOMEM);
- return -ENOMEM;
+ ret = cbd.ret;
+ return ret;
}
ctrl->last_tid++;
}
@@ -345,33 +360,56 @@ void slim_return_tx(struct slim_controller *ctrl, int err)
else
cur.cb(cur.ctx, err);
up(&ctrl->tx_sem);
+ if (!cur.clk_pause && (!cur.need_tid || err)) {
+ /**
+ * remove runtime-pm vote if this was TX only, or
+ * if there was error during this transaction
+ */
+ pm_runtime_mark_last_busy(ctrl->dev.parent);
+ pm_runtime_put_autosuspend(ctrl->dev.parent);
+ }
}
EXPORT_SYMBOL_GPL(slim_return_tx);

void *slim_get_tx(struct slim_controller *ctrl, struct slim_msg_txn *txn,
- bool need_tid)
+ bool need_tid, bool clk_pause)
{
unsigned long flags;
int ret, idx;

+ if (!clk_pause) {
+ ret = pm_runtime_get_sync(ctrl->dev.parent);
+
+ if (ctrl->sched.clk_state != SLIM_CLK_ACTIVE) {
+ dev_err(&ctrl->dev, "ctrl wrong state:%d, ret:%d\n",
+ ctrl->sched.clk_state, ret);
+ goto slim_tx_err;
+ }
+ }
+
ret = down_interruptible(&ctrl->tx_sem);
if (ret < 0) {
dev_err(&ctrl->dev, "TX semaphore down returned:%d", ret);
- return NULL;
+ goto slim_tx_err;
}
spin_lock_irqsave(&ctrl->tx.lock, flags);
if (((ctrl->tx.head + 1) % ctrl->tx.n) == ctrl->tx.tail) {
spin_unlock_irqrestore(&ctrl->tx.lock, flags);
dev_err(&ctrl->dev, "controller TX buf unavailable");
up(&ctrl->tx_sem);
- return NULL;
+ goto slim_tx_err;
}
idx = ctrl->tx.tail;
ctrl->tx.tail = (ctrl->tx.tail + 1) % ctrl->tx.n;
ctrl->pending_wr[idx].cb = txn->msg->comp_cb;
ctrl->pending_wr[idx].ctx = txn->msg->ctx;
ctrl->pending_wr[idx].need_tid = need_tid;
+ ctrl->pending_wr[idx].clk_pause = clk_pause;
spin_unlock_irqrestore(&ctrl->tx.lock, flags);
return ctrl->tx.base + (idx * ctrl->tx.sl_sz);
+slim_tx_err:
+ pm_runtime_mark_last_busy(ctrl->dev.parent);
+ pm_runtime_put_autosuspend(ctrl->dev.parent);
+ return NULL;
}
EXPORT_SYMBOL_GPL(slim_get_tx);
diff --git a/drivers/slimbus/slim-sched.c b/drivers/slimbus/slim-sched.c
new file mode 100644
index 0000000..301690d
--- /dev/null
+++ b/drivers/slimbus/slim-sched.c
@@ -0,0 +1,122 @@
+/* Copyright (c) 2011-2016, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/errno.h>
+#include <linux/slimbus.h>
+
+/**
+ * slim_ctrl_clk_pause: Called by slimbus controller to enter/exit 'clock pause'
+ * 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.
+ * @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.
+ * 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, 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 < ctrl->last_tid; i++) {
+ /* Pending response for a message */
+ if (ctrl->tid_tbl[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_processtxn(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_processtxn(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_processtxn(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);
+
diff --git a/include/linux/slimbus.h b/include/linux/slimbus.h
index 3fd626c..55f2b71 100644
--- a/include/linux/slimbus.h
+++ b/include/linux/slimbus.h
@@ -117,11 +117,21 @@ struct slim_addrt {
#define SLIM_MSG_MC_REPLY_VALUE 0x64
#define SLIM_MSG_MC_CHANGE_VALUE 0x68

+/* Clock pause Reconfiguration messages */
+#define SLIM_MSG_MC_BEGIN_RECONFIGURATION 0x40
+#define SLIM_MSG_MC_NEXT_PAUSE_CLOCK 0x4A
+#define SLIM_MSG_MC_RECONFIGURE_NOW 0x5F
+
/* Destination type Values */
#define SLIM_MSG_DEST_LOGICALADDR 0
#define SLIM_MSG_DEST_ENUMADDR 1
#define SLIM_MSG_DEST_BROADCAST 3

+/* Clock pause values per slimbus spec */
+#define SLIM_CLK_FAST 0
+#define SLIM_CLK_CONST_PHASE 1
+#define SLIM_CLK_UNSPECIFIED 2
+
/**
* struct slim_val_inf: Slimbus value or information element
* @start_offset: Specifies starting offset in information/value element map
@@ -205,11 +215,46 @@ struct slim_ctrl_buf {
* @cb: callback for this transfer
* @ctx: contex for the callback function
* @need_tid: True if this transfer need Transaction ID
+ * @clk_pause: True if this transfer is part of clock-pause sequence
*/
struct slim_pending {
void (*cb)(void *ctx, int err);
void *ctx;
bool need_tid;
+ bool clk_pause;
+};
+
+/**
+ * enum slim_clk_state: Slimbus controller's clock state used internally for
+ * maintaining current clock state.
+ * @SLIM_CLK_ACTIVE: Slimbus clock is active
+ * @SLIM_CLK_ENTERING_PAUSE: Slimbus clock pause sequence is being sent on the
+ * bus. If this succeeds, state changes to SLIM_CLK_PAUSED. If the
+ * transition fails, state changes back to SLIM_CLK_ACTIVE
+ * @SLIM_CLK_PAUSED: Slimbus controller clock has paused.
+ */
+enum slim_clk_state {
+ SLIM_CLK_ACTIVE,
+ SLIM_CLK_ENTERING_PAUSE,
+ SLIM_CLK_PAUSED,
+};
+
+/**
+ * struct slim_sched: Framework uses this structure internally for scheduling.
+ * @clk_state: Controller's clock state from enum slim_clk_state
+ * @pause_comp: Signals completion of clock pause sequence. This is useful when
+ * client tries to call slimbus transaction when controller is entering
+ * clock pause.
+ * @m_reconf: This mutex is held until current reconfiguration (data channel
+ * scheduling, message bandwidth reservation) is done. Message APIs can
+ * use the bus concurrently when this mutex is held since elemental access
+ * messages can be sent on the bus when reconfiguration is in progress.
+ */
+struct slim_sched {
+ int clkgear;
+ enum slim_clk_state clk_state;
+ struct completion pause_comp;
+ struct mutex m_reconf;
};

/**
@@ -256,6 +301,7 @@ struct slim_pending {
* @pending_wr: Pending write transactions to be acknowledged by controller
* @tx_sem: Semaphore for available TX buffers for this controller
* @last_tid: Last used entry for TID transactions
+ * @sched: scheduler structure used by the controller
* @dev_released: completion used to signal when sysfs has released this
* controller so that it can be deleted during shutdown
* @xfer_msg: Transfer a message on this controller (this can be a broadcast
@@ -267,6 +313,9 @@ struct slim_pending {
* @get_laddr: It is possible that controller needs to set fixed logical
* address table and get_laddr can be used in that case so that controller
* can do this assignment.
+ * @wakeup: This function pointer implements controller-specific procedure
+ * to wake it up from clock-pause. Framework will call this to bring
+ * the controller out of clock pause.
*/
struct slim_controller {
struct device dev;
@@ -288,6 +337,7 @@ struct slim_controller {
struct slim_ctrl_buf rx;
struct slim_pending *pending_wr;
struct semaphore tx_sem;
+ struct slim_sched sched;
struct completion dev_released;
int (*xfer_msg)(struct slim_controller *ctrl,
struct slim_msg_txn *tx, void *buf);
@@ -295,6 +345,7 @@ struct slim_controller {
struct slim_eaddr *ea, u8 laddr);
int (*get_laddr)(struct slim_controller *ctrl,
struct slim_eaddr *ea, u8 *laddr);
+ int (*wakeup)(struct slim_controller *ctrl);
};

#define to_slim_controller(d) container_of(d, struct slim_controller, dev)
@@ -594,7 +645,7 @@ void *slim_get_rx(struct slim_controller *ctrl);
int slim_return_rx(struct slim_controller *ctrl, void *buf);

void *slim_get_tx(struct slim_controller *ctrl, struct slim_msg_txn *txn,
- bool need_tid);
+ bool need_tid, bool clk_pause);

void slim_return_tx(struct slim_controller *ctrl, int err);

@@ -608,4 +659,20 @@ static inline bool slim_tid_txn(u8 mt, u8 mc)
}
/* end of message apis */

+/**
+ * slim_ctrl_clk_pause: Called by slimbus controller to enter/exit 'clock pause'
+ * 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.
+ * @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.
+ * 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);
+
#endif /* _LINUX_SLIMBUS_H */
--
1.8.2.1