[PATCH v3 0/7] Updates to MHI channel handling

[PATCH v3 0/7] Updates to MHI channel handling

[Bhaumik Bhatt]

MHI specification shows a state machine with support for STOP channel command
and the validity of certain state transitions. MHI host currently does not
provide any mechanism to stop a channel and restart it without resetting it.
There are also times when the device moves on to a different execution
environment while client drivers on the host are unaware of it and still
attempt to reset the channels facing unnecessary timeouts.

This series addresses the above areas to provide support for stopping an MHI
channel, resuming it back, improved documentation and improving upon channel
state machine handling in general.

This set of patches was tested on arm64 architecture.

v3:
-Updated documentation for channel transfer APIs to highlight differences
-Create separate patch for "allowing channel to be disabled from stopped state"

v2:
-Renamed the newly introduced APIs to mhi_start_transfer() / mhi_stop_transfer()
-Added improved documentation to avoid confusion with the new APIs
-Removed the __ prefix from mhi_unprepare_channel() API for consistency.

Bhaumik Bhatt (7):
  bus: mhi: core: Allow receiving a STOP channel command response
  bus: mhi: core: Allow channel to be disabled from stopped state
  bus: mhi: core: Improvements to the channel handling state machine
  bus: mhi: core: Add support to stop or start channel data transfers
  bus: mhi: core: Check execution environment for channel before issuing
    reset
  bus: mhi: core: Remove __ prefix for MHI channel unprepare function
  bus: mhi: Improve documentation on channel transfer setup APIs

 drivers/bus/mhi/core/init.c     |   9 +-
 drivers/bus/mhi/core/internal.h |  12 +++
 drivers/bus/mhi/core/main.c     | 229 +++++++++++++++++++++++++++-------------
 include/linux/mhi.h             |  45 +++++++-
 4 files changed, 220 insertions(+), 75 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 1/7] bus: mhi: core: Allow receiving a STOP channel command response

[Bhaumik Bhatt]

Add support to receive the response to a STOP channel command to the
MHI bus. If a client would like to STOP a channel instead of issuing
a RESET to it, this would provide support for it.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 702c31b..a7bb8a7 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1193,6 +1193,11 @@ int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
 		cmd_tre->dword[0] = MHI_TRE_CMD_RESET_DWORD0;
 		cmd_tre->dword[1] = MHI_TRE_CMD_RESET_DWORD1(chan);
 		break;
+	case MHI_CMD_STOP_CHAN:
+		cmd_tre->ptr = MHI_TRE_CMD_STOP_PTR;
+		cmd_tre->dword[0] = MHI_TRE_CMD_STOP_DWORD0;
+		cmd_tre->dword[1] = MHI_TRE_CMD_STOP_DWORD1(chan);
+		break;
 	case MHI_CMD_START_CHAN:
 		cmd_tre->ptr = MHI_TRE_CMD_START_PTR;
 		cmd_tre->dword[0] = MHI_TRE_CMD_START_DWORD0;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 2/7] bus: mhi: core: Allow channel to be disabled from stopped state

[Bhaumik Bhatt]

If a channel was explicitly stopped but not reset, allow it to
move to a disabled state so the channel context can be cleaned
up. As the channel remained in a stopped state, its context was
not reset and cleared, which needs to be done if a client driver
module is unloaded or a device crash occurs.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index f0697f4..e7b9a90 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -1288,7 +1288,8 @@ static int mhi_driver_remove(struct device *dev)
 
 		mutex_lock(&mhi_chan->mutex);
 
-		if (ch_state[dir] == MHI_CH_STATE_ENABLED &&
+		if ((ch_state[dir] == MHI_CH_STATE_ENABLED ||
+		    ch_state[dir] == MHI_CH_STATE_STOP) &&
 		    !mhi_chan->offload_ch)
 			mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 3/7] bus: mhi: core: Improvements to the channel handling state machine

[Bhaumik Bhatt]

Add support to enable sending the stop channel command and
improve the channel handling state machine such that all commands
go through a common function. This can help ensure that the state
machine is not violated in any way and adheres to the MHI
specification.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/init.c     |   6 ++
 drivers/bus/mhi/core/internal.h |  12 +++
 drivers/bus/mhi/core/main.c     | 166 +++++++++++++++++++++++-----------------
 3 files changed, 114 insertions(+), 70 deletions(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index e7b9a90..4f6d69c 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -54,6 +54,12 @@ const char * const mhi_state_str[MHI_STATE_MAX] = {
 	[MHI_STATE_SYS_ERR] = "SYS_ERR",
 };
 
+const char * const mhi_ch_state_type_str[MHI_CH_STATE_TYPE_MAX] = {
+	[MHI_CH_STATE_TYPE_RESET] = "RESET",
+	[MHI_CH_STATE_TYPE_STOP] = "STOP",
+	[MHI_CH_STATE_TYPE_START] = "START",
+};
+
 static const char * const mhi_pm_state_str[] = {
 	[MHI_PM_STATE_DISABLE] = "DISABLE",
 	[MHI_PM_STATE_POR] = "POR",
diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
index 6f80ec3..251d7d7 100644
--- a/drivers/bus/mhi/core/internal.h
+++ b/drivers/bus/mhi/core/internal.h
@@ -369,6 +369,18 @@ enum mhi_ch_state {
 	MHI_CH_STATE_ERROR = 0x5,
 };
 
+enum mhi_ch_state_type {
+	MHI_CH_STATE_TYPE_RESET,
+	MHI_CH_STATE_TYPE_STOP,
+	MHI_CH_STATE_TYPE_START,
+	MHI_CH_STATE_TYPE_MAX,
+};
+
+extern const char * const mhi_ch_state_type_str[MHI_CH_STATE_TYPE_MAX];
+#define TO_CH_STATE_TYPE_STR(state) (((state) >= MHI_CH_STATE_TYPE_MAX) ? \
+				     "INVALID_STATE" : \
+				     mhi_ch_state_type_str[state])
+
 #define MHI_INVALID_BRSTMODE(mode) (mode != MHI_DB_BRST_DISABLE && \
 				    mode != MHI_DB_BRST_ENABLE)
 
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index a7bb8a7..4cc5ced 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1219,56 +1219,118 @@ int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
 	return 0;
 }
 
-static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
-				    struct mhi_chan *mhi_chan)
+static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
+				    struct mhi_chan *mhi_chan,
+				    enum mhi_ch_state_type to_state)
 {
-	int ret;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+	enum mhi_cmd_type cmd = MHI_CMD_NOP;
+	int ret = -EIO;
+
+	dev_dbg(dev, "Updating channel %s(%d) state to: %s\n", mhi_chan->name,
+		mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+	switch (to_state) {
+	case MHI_CH_STATE_TYPE_RESET:
+		write_lock_irq(&mhi_chan->lock);
+		if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
+		    mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
+		    mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
+			write_unlock_irq(&mhi_chan->lock);
+			goto exit_invalid_state;
+		}
+		mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
+		write_unlock_irq(&mhi_chan->lock);
 
-	dev_dbg(dev, "Entered: unprepare channel:%d\n", mhi_chan->chan);
+		cmd = MHI_CMD_RESET_CHAN;
+		break;
+	case MHI_CH_STATE_TYPE_STOP:
+		if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
+			goto exit_invalid_state;
 
-	/* no more processing events for this channel */
-	mutex_lock(&mhi_chan->mutex);
-	write_lock_irq(&mhi_chan->lock);
-	if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
-	    mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
-		write_unlock_irq(&mhi_chan->lock);
-		mutex_unlock(&mhi_chan->mutex);
-		return;
+		cmd = MHI_CMD_STOP_CHAN;
+		break;
+	case MHI_CH_STATE_TYPE_START:
+		if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
+		    mhi_chan->ch_state != MHI_CH_STATE_DISABLED)
+			goto exit_invalid_state;
+
+		cmd = MHI_CMD_START_CHAN;
+		break;
+	default:
+		goto exit_invalid_state;
 	}
 
-	mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
-	write_unlock_irq(&mhi_chan->lock);
+	/* bring host and device out of suspended states */
+	ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
+	if (ret)
+		return ret;
+	mhi_cntrl->runtime_get(mhi_cntrl);
 
 	reinit_completion(&mhi_chan->completion);
-	read_lock_bh(&mhi_cntrl->pm_lock);
-	if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
-		read_unlock_bh(&mhi_cntrl->pm_lock);
-		goto error_invalid_state;
+	ret = mhi_send_cmd(mhi_cntrl, mhi_chan, cmd);
+	if (ret) {
+		dev_err(dev, "Failed to send %s(%d) %s command\n",
+			mhi_chan->name, mhi_chan->chan,
+			TO_CH_STATE_TYPE_STR(to_state));
+		goto exit_command_failure;
 	}
 
-	mhi_cntrl->wake_toggle(mhi_cntrl);
-	read_unlock_bh(&mhi_cntrl->pm_lock);
+	ret = wait_for_completion_timeout(&mhi_chan->completion,
+				       msecs_to_jiffies(mhi_cntrl->timeout_ms));
+	if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS) {
+		dev_err(dev, "Failed to receive %s(%d) %s command completion\n",
+			mhi_chan->name, mhi_chan->chan,
+			TO_CH_STATE_TYPE_STR(to_state));
+		ret = -EIO;
+		goto exit_command_failure;
+	}
 
-	mhi_cntrl->runtime_get(mhi_cntrl);
+	ret = 0;
+
+	if (to_state != MHI_CH_STATE_TYPE_RESET) {
+		write_lock_irq(&mhi_chan->lock);
+		mhi_chan->ch_state = (to_state == MHI_CH_STATE_TYPE_START) ?
+				      MHI_CH_STATE_ENABLED : MHI_CH_STATE_STOP;
+		write_unlock_irq(&mhi_chan->lock);
+	}
+
+	dev_dbg(dev, "Channel %s(%d) state change to %s successful\n",
+		mhi_chan->name, mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+exit_command_failure:
 	mhi_cntrl->runtime_put(mhi_cntrl);
-	ret = mhi_send_cmd(mhi_cntrl, mhi_chan, MHI_CMD_RESET_CHAN);
-	if (ret)
-		goto error_invalid_state;
+	mhi_device_put(mhi_cntrl->mhi_dev);
 
-	/* even if it fails we will still reset */
-	ret = wait_for_completion_timeout(&mhi_chan->completion,
-				msecs_to_jiffies(mhi_cntrl->timeout_ms));
-	if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS)
-		dev_err(dev,
-			"Failed to receive cmd completion, still resetting\n");
+	return ret;
+
+exit_invalid_state:
+	dev_err(dev, "Channel %s(%d) update to %s not allowed\n",
+		mhi_chan->name, mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+	return -EINVAL;
+}
+
+static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+				    struct mhi_chan *mhi_chan)
+{
+	int ret;
+	struct device *dev = &mhi_cntrl->mhi_dev->dev;
+
+	/* no more processing events for this channel */
+	mutex_lock(&mhi_chan->mutex);
+
+	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+				       MHI_CH_STATE_TYPE_RESET);
+	if (ret)
+		dev_err(dev, "Failed to reset channel, still resetting\n");
 
-error_invalid_state:
 	if (!mhi_chan->offload_ch) {
 		mhi_reset_chan(mhi_cntrl, mhi_chan);
 		mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
 	}
-	dev_dbg(dev, "chan:%d successfully resetted\n", mhi_chan->chan);
+	dev_dbg(dev, "chan:%d successfully reset\n", mhi_chan->chan);
+
 	mutex_unlock(&mhi_chan->mutex);
 }
 
@@ -1278,8 +1340,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 	int ret = 0;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
 
-	dev_dbg(dev, "Preparing channel: %d\n", mhi_chan->chan);
-
 	if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
 		dev_err(dev,
 			"Current EE: %s Required EE Mask: 0x%x for chan: %s\n",
@@ -1290,14 +1350,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 
 	mutex_lock(&mhi_chan->mutex);
 
-	/* If channel is not in disable state, do not allow it to start */
-	if (mhi_chan->ch_state != MHI_CH_STATE_DISABLED) {
-		ret = -EIO;
-		dev_dbg(dev, "channel: %d is not in disabled state\n",
-			mhi_chan->chan);
-		goto error_init_chan;
-	}
-
 	/* Check of client manages channel context for offload channels */
 	if (!mhi_chan->offload_ch) {
 		ret = mhi_init_chan_ctxt(mhi_cntrl, mhi_chan);
@@ -1305,34 +1357,11 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 			goto error_init_chan;
 	}
 
-	reinit_completion(&mhi_chan->completion);
-	read_lock_bh(&mhi_cntrl->pm_lock);
-	if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
-		read_unlock_bh(&mhi_cntrl->pm_lock);
-		ret = -EIO;
-		goto error_pm_state;
-	}
-
-	mhi_cntrl->wake_toggle(mhi_cntrl);
-	read_unlock_bh(&mhi_cntrl->pm_lock);
-	mhi_cntrl->runtime_get(mhi_cntrl);
-	mhi_cntrl->runtime_put(mhi_cntrl);
-
-	ret = mhi_send_cmd(mhi_cntrl, mhi_chan, MHI_CMD_START_CHAN);
+	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+				       MHI_CH_STATE_TYPE_START);
 	if (ret)
 		goto error_pm_state;
 
-	ret = wait_for_completion_timeout(&mhi_chan->completion,
-				msecs_to_jiffies(mhi_cntrl->timeout_ms));
-	if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS) {
-		ret = -EIO;
-		goto error_pm_state;
-	}
-
-	write_lock_irq(&mhi_chan->lock);
-	mhi_chan->ch_state = MHI_CH_STATE_ENABLED;
-	write_unlock_irq(&mhi_chan->lock);
-
 	/* Pre-allocate buffer for xfer ring */
 	if (mhi_chan->pre_alloc) {
 		int nr_el = get_nr_avail_ring_elements(mhi_cntrl,
@@ -1370,9 +1399,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 
 	mutex_unlock(&mhi_chan->mutex);
 
-	dev_dbg(dev, "Chan: %d successfully moved to start state\n",
-		mhi_chan->chan);
-
 	return 0;
 
 error_pm_state:
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 4/7] bus: mhi: core: Add support to stop or start channel data transfers

[Bhaumik Bhatt]

Some MHI client drivers may want to request a pause or halt of
data transfer activity on their channels. Support for this does
not exist and must be introduced, wherein the channel context is
not reset or cleared but only the STOP channel command is issued.
This would need to be paired with an API that allows resuming the
data transfer activity on channels by use of the START channel
command. This API assumes that the context information is already
setup. Enable this using two new APIs, mhi_start_transfer() and
mhi_stop_transfer().

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/mhi.h         | 19 +++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 4cc5ced..2e4b34a 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1552,6 +1552,47 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
 }
 EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
 
+static int mhi_update_transfer_state(struct mhi_device *mhi_dev,
+				     enum mhi_ch_state_type to_state)
+{
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	struct mhi_chan *mhi_chan;
+	int dir, ret;
+
+	for (dir = 0; dir < 2; dir++) {
+		mhi_chan = dir ? mhi_dev->ul_chan : mhi_dev->dl_chan;
+
+		if (!mhi_chan)
+			continue;
+
+		/*
+		 * Bail out if one of the channels fail as client will reset
+		 * both upon failure
+		 */
+		mutex_lock(&mhi_chan->mutex);
+		ret = mhi_update_channel_state(mhi_cntrl, mhi_chan, to_state);
+		if (ret) {
+			mutex_unlock(&mhi_chan->mutex);
+			return ret;
+		}
+		mutex_unlock(&mhi_chan->mutex);
+	}
+
+	return 0;
+}
+
+int mhi_stop_transfer(struct mhi_device *mhi_dev)
+{
+	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
+}
+EXPORT_SYMBOL_GPL(mhi_stop_transfer);
+
+int mhi_start_transfer(struct mhi_device *mhi_dev)
+{
+	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
+}
+EXPORT_SYMBOL_GPL(mhi_start_transfer);
+
 int mhi_poll(struct mhi_device *mhi_dev, u32 budget)
 {
 	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index aa9757e..35779a0 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -704,6 +704,25 @@ int mhi_prepare_for_transfer(struct mhi_device *mhi_dev);
 void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
 
 /**
+ * mhi_stop_transfer - Pauses ongoing channel activity by issuing the STOP
+ *                     channel command to both UL and DL channels. This command
+ *                     does not reset the channel context and the client drivers
+ *                     can issue mhi_start_transfer to resume activity.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_stop_transfer(struct mhi_device *mhi_dev);
+
+/**
+ * mhi_start_transfer - Resumes channel activity by issuing the START channel
+ *                      command to both UL and DL channels. This command assumes
+ *                      the channel context is already setup and the client
+ *                      drivers can issue mhi_stop_transfer to pause activity if
+ *                      required.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_start_transfer(struct mhi_device *mhi_dev);
+
+/**
  * mhi_poll - Poll for any available data in DL direction
  * @mhi_dev: Device associated with the channels
  * @budget: # of events to process
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 5/7] bus: mhi: core: Check execution environment for channel before issuing reset

[Bhaumik Bhatt]

A client can attempt to unprepare certain channels for transfer even
after the execution environment they are supposed to run in has changed.
In the event that happens, the device need not be notified of the reset
and the host can proceed with clean up for the channel context and
memory allocated for it on the host.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 2e4b34a..40d15ef 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1320,11 +1320,24 @@ static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
 	/* no more processing events for this channel */
 	mutex_lock(&mhi_chan->mutex);
 
+	if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
+		dev_err(dev,
+			"Current EE: %s Required EE Mask: 0x%x for chan: %s\n",
+			TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask,
+			mhi_chan->name);
+		goto exit_unprepare_channel;
+	}
+
 	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
 				       MHI_CH_STATE_TYPE_RESET);
 	if (ret)
 		dev_err(dev, "Failed to reset channel, still resetting\n");
 
+exit_unprepare_channel:
+	write_lock_irq(&mhi_chan->lock);
+	mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
+	write_unlock_irq(&mhi_chan->lock);
+
 	if (!mhi_chan->offload_ch) {
 		mhi_reset_chan(mhi_cntrl, mhi_chan);
 		mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 6/7] bus: mhi: core: Remove __ prefix for MHI channel unprepare function

[Bhaumik Bhatt]

The __mhi_unprepare_channel() API does not require the __ prefix.
Get rid of it and make the internal function consistent with the
other function names.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/core/main.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 40d15ef..566507d 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1311,8 +1311,8 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
 	return -EINVAL;
 }
 
-static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
-				    struct mhi_chan *mhi_chan)
+static void mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+				  struct mhi_chan *mhi_chan)
 {
 	int ret;
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -1425,7 +1425,7 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 
 error_pre_alloc:
 	mutex_unlock(&mhi_chan->mutex);
-	__mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+	mhi_unprepare_channel(mhi_cntrl, mhi_chan);
 
 	return ret;
 }
@@ -1542,7 +1542,7 @@ int mhi_prepare_for_transfer(struct mhi_device *mhi_dev)
 		if (!mhi_chan)
 			continue;
 
-		__mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+		mhi_unprepare_channel(mhi_cntrl, mhi_chan);
 	}
 
 	return ret;
@@ -1560,7 +1560,7 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
 		if (!mhi_chan)
 			continue;
 
-		__mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+		mhi_unprepare_channel(mhi_cntrl, mhi_chan);
 	}
 }
 EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 7/7] bus: mhi: Improve documentation on channel transfer setup APIs

[Bhaumik Bhatt]

The mhi_prepare_for_transfer() and mhi_unprepare_from_transfer()
APIs could use better explanation, especially with the addition
of two new APIs to start and stop the transfers on channels. Add
better set of information for those APIs.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 include/linux/mhi.h | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 35779a0..bd229da 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -692,13 +692,35 @@ int mhi_device_get_sync(struct mhi_device *mhi_dev);
 void mhi_device_put(struct mhi_device *mhi_dev);
 
 /**
- * mhi_prepare_for_transfer - Setup channel for data transfer
+ * mhi_prepare_for_transfer - Setup UL and DL channels for data transfer.
+ *                            Allocate and initialize the channel context and
+ *                            also issue the START channel command to both
+ *                            channels. Channels can be started only if both
+ *                            host and device execution environments match and
+ *                            channels are in a DISABLED state. Calling the
+ *                            mhi_start_transfer() function is not required
+ *                            afterwards as channels are already started. This
+ *                            function also initializes the channel context
+ *                            whereas mhi_start_transfer() can only be used to
+ *                            issue the start channel command once the context
+ *                            is setup.
  * @mhi_dev: Device associated with the channels
  */
 int mhi_prepare_for_transfer(struct mhi_device *mhi_dev);
 
 /**
- * mhi_unprepare_from_transfer - Unprepare the channels
+ * mhi_unprepare_from_transfer - Reset UL and DL channels for data transfer.
+ *                               Issue the RESET channel command and let the
+ *                               device clean-up the context so no incoming
+ *                               transfers are seen on the host. Free memory
+ *                               associated with the context on host. If device
+ *                               is unresponsive, only perform a host side
+ *                               clean-up. Channels can be reset only if both
+ *                               host and device execution environments match
+ *                               and channels are in an ENABLED, STOPPED or
+ *                               SUSPENDED state. Calling mhi_stop_transfer() is
+ *                               not required before calling this function as it
+ *                               will only stop transfers, not reset channels.
  * @mhi_dev: Device associated with the channels
  */
 void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 6/7] bus: mhi: core: Remove __ prefix for MHI channel unprepare function

[Hemant Kumar]

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> The __mhi_unprepare_channel() API does not require the __ prefix.
> Get rid of it and make the internal function consistent with the
> other function names.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 1/7] bus: mhi: core: Allow receiving a STOP channel command response

[Hemant Kumar]

Hi Bhaumik,

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> Add support to receive the response to a STOP channel command to the
How about saying "Add support to send the STOP channel command ?
> MHI bus. If a client would like to STOP a channel instead of issuing
> a RESET to it, this would provide support for it.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---
>   drivers/bus/mhi/core/main.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 702c31b..a7bb8a7 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1193,6 +1193,11 @@ int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
>   		cmd_tre->dword[0] = MHI_TRE_CMD_RESET_DWORD0;
>   		cmd_tre->dword[1] = MHI_TRE_CMD_RESET_DWORD1(chan);
>   		break;
> +	case MHI_CMD_STOP_CHAN:
> +		cmd_tre->ptr = MHI_TRE_CMD_STOP_PTR;
> +		cmd_tre->dword[0] = MHI_TRE_CMD_STOP_DWORD0;
> +		cmd_tre->dword[1] = MHI_TRE_CMD_STOP_DWORD1(chan);
> +		break;
>   	case MHI_CMD_START_CHAN:
>   		cmd_tre->ptr = MHI_TRE_CMD_START_PTR;
>   		cmd_tre->dword[0] = MHI_TRE_CMD_START_DWORD0;
> 

Thanks,
Hemant
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 2/7] bus: mhi: core: Allow channel to be disabled from stopped state

[Hemant Kumar]

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> If a channel was explicitly stopped but not reset, allow it to
> move to a disabled state so the channel context can be cleaned
> up. As the channel remained in a stopped state, its context was
> not reset and cleared, which needs to be done if a client driver
> module is unloaded or a device crash occurs.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---

Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 4/7] bus: mhi: core: Add support to stop or start channel data transfers

[Hemant Kumar]

Hi Bhaumik,

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> Some MHI client drivers may want to request a pause or halt of
> data transfer activity on their channels. Support for this does
> not exist and must be introduced, wherein the channel context is
> not reset or cleared but only the STOP channel command is issued.
> This would need to be paired with an API that allows resuming the
> data transfer activity on channels by use of the START channel
> command. This API assumes that the context information is already

is it a better option to make sure channel context is setup as this is 
an exported API. Hence check for channel context bail out in case 
channel context is not setup with an err msg ?

> setup. Enable this using two new APIs, mhi_start_transfer() and
> mhi_stop_transfer().
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---
>   drivers/bus/mhi/core/main.c | 41 +++++++++++++++++++++++++++++++++++++++++
>   include/linux/mhi.h         | 19 +++++++++++++++++++
>   2 files changed, 60 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 4cc5ced..2e4b34a 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1552,6 +1552,47 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
>   }
>   EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
>   
> +static int mhi_update_transfer_state(struct mhi_device *mhi_dev,
> +				     enum mhi_ch_state_type to_state)
> +{
> +	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
> +	struct mhi_chan *mhi_chan;
> +	int dir, ret;
> +
> +	for (dir = 0; dir < 2; dir++) {
> +		mhi_chan = dir ? mhi_dev->ul_chan : mhi_dev->dl_chan;
> +
> +		if (!mhi_chan)
> +			continue;
> +
> +		/*
> +		 * Bail out if one of the channels fail as client will reset
> +		 * both upon failure
> +		 */
> +		mutex_lock(&mhi_chan->mutex);
> +		ret = mhi_update_channel_state(mhi_cntrl, mhi_chan, to_state);
> +		if (ret) {
> +			mutex_unlock(&mhi_chan->mutex);
> +			return ret;
> +		}
> +		mutex_unlock(&mhi_chan->mutex);
> +	}
> +
> +	return 0;
> +}
> +
> +int mhi_stop_transfer(struct mhi_device *mhi_dev)
> +{
> +	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
> +}
> +EXPORT_SYMBOL_GPL(mhi_stop_transfer);
> +
> +int mhi_start_transfer(struct mhi_device *mhi_dev)
> +{
> +	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
> +}
> +EXPORT_SYMBOL_GPL(mhi_start_transfer);
> +
>   int mhi_poll(struct mhi_device *mhi_dev, u32 budget)
>   {
>   	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index aa9757e..35779a0 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -704,6 +704,25 @@ int mhi_prepare_for_transfer(struct mhi_device *mhi_dev);
>   void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
>   
>   /**
> + * mhi_stop_transfer - Pauses ongoing channel activity by issuing the STOP
> + *                     channel command to both UL and DL channels. This command
> + *                     does not reset the channel context and the client drivers
> + *                     can issue mhi_start_transfer to resume activity.
> + * @mhi_dev: Device associated with the channels
> + */
> +int mhi_stop_transfer(struct mhi_device *mhi_dev);
> +
> +/**
> + * mhi_start_transfer - Resumes channel activity by issuing the START channel
> + *                      command to both UL and DL channels. This command assumes
> + *                      the channel context is already setup and the client
> + *                      drivers can issue mhi_stop_transfer to pause activity if
> + *                      required.
> + * @mhi_dev: Device associated with the channels
> + */
> +int mhi_start_transfer(struct mhi_device *mhi_dev);
> +
> +/**
>    * mhi_poll - Poll for any available data in DL direction
>    * @mhi_dev: Device associated with the channels
>    * @budget: # of events to process
> 
Overall change looks good.

Thanks,
Hemant
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 3/7] bus: mhi: core: Improvements to the channel handling state machine

[Hemant Kumar]

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> Add support to enable sending the stop channel command and
> improve the channel handling state machine such that all commands
> go through a common function. This can help ensure that the state
> machine is not violated in any way and adheres to the MHI
> specification.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 5/7] bus: mhi: core: Check execution environment for channel before issuing reset

[Hemant Kumar]

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> A client can attempt to unprepare certain channels for transfer even
> after the execution environment they are supposed to run in has changed.
> In the event that happens, the device need not be notified of the reset
> and the host can proceed with clean up for the channel context and
> memory allocated for it on the host.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>

Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 7/7] bus: mhi: Improve documentation on channel transfer setup APIs

[Hemant Kumar]

On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
> The mhi_prepare_for_transfer() and mhi_unprepare_from_transfer()
> APIs could use better explanation, especially with the addition
> of two new APIs to start and stop the transfers on channels. Add
> better set of information for those APIs.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 1/7] bus: mhi: core: Allow receiving a STOP channel command response

[Bhaumik Bhatt]

On 2020-12-02 04:15 PM, Hemant Kumar wrote:
> Hi Bhaumik,
> 
> On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
>> Add support to receive the response to a STOP channel command to the
> How about saying "Add support to send the STOP channel command ?
Addressed in v4.
>> MHI bus. If a client would like to STOP a channel instead of issuing
>> a RESET to it, this would provide support for it.
>> 
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>>   drivers/bus/mhi/core/main.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>> 
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 702c31b..a7bb8a7 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -1193,6 +1193,11 @@ int mhi_send_cmd(struct mhi_controller 
>> *mhi_cntrl,
>>   		cmd_tre->dword[0] = MHI_TRE_CMD_RESET_DWORD0;
>>   		cmd_tre->dword[1] = MHI_TRE_CMD_RESET_DWORD1(chan);
>>   		break;
>> +	case MHI_CMD_STOP_CHAN:
>> +		cmd_tre->ptr = MHI_TRE_CMD_STOP_PTR;
>> +		cmd_tre->dword[0] = MHI_TRE_CMD_STOP_DWORD0;
>> +		cmd_tre->dword[1] = MHI_TRE_CMD_STOP_DWORD1(chan);
>> +		break;
>>   	case MHI_CMD_START_CHAN:
>>   		cmd_tre->ptr = MHI_TRE_CMD_START_PTR;
>>   		cmd_tre->dword[0] = MHI_TRE_CMD_START_DWORD0;
>> 
> 
> Thanks,
> Hemant

Thanks,
Bhaumik
---
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Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v3 4/7] bus: mhi: core: Add support to stop or start channel data transfers

[Bhaumik Bhatt]

On 2020-12-02 04:33 PM, Hemant Kumar wrote:
> Hi Bhaumik,
> 
> On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
>> Some MHI client drivers may want to request a pause or halt of
>> data transfer activity on their channels. Support for this does
>> not exist and must be introduced, wherein the channel context is
>> not reset or cleared but only the STOP channel command is issued.
>> This would need to be paired with an API that allows resuming the
>> data transfer activity on channels by use of the START channel
>> command. This API assumes that the context information is already
> 
> is it a better option to make sure channel context is setup as this is
> an exported API. Hence check for channel context bail out in case
> channel context is not setup with an err msg ?
> 
This is a better method, yes. Addressed in v4.
>> setup. Enable this using two new APIs, mhi_start_transfer() and
>> mhi_stop_transfer().
>> 
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>>   drivers/bus/mhi/core/main.c | 41 
>> +++++++++++++++++++++++++++++++++++++++++
>>   include/linux/mhi.h         | 19 +++++++++++++++++++
>>   2 files changed, 60 insertions(+)
>> 
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 4cc5ced..2e4b34a 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -1552,6 +1552,47 @@ void mhi_unprepare_from_transfer(struct 
>> mhi_device *mhi_dev)
>>   }
>>   EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
>>   +static int mhi_update_transfer_state(struct mhi_device *mhi_dev,
>> +				     enum mhi_ch_state_type to_state)
>> +{
>> +	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>> +	struct mhi_chan *mhi_chan;
>> +	int dir, ret;
>> +
>> +	for (dir = 0; dir < 2; dir++) {
>> +		mhi_chan = dir ? mhi_dev->ul_chan : mhi_dev->dl_chan;
>> +
>> +		if (!mhi_chan)
>> +			continue;
>> +
>> +		/*
>> +		 * Bail out if one of the channels fail as client will reset
>> +		 * both upon failure
>> +		 */
>> +		mutex_lock(&mhi_chan->mutex);
>> +		ret = mhi_update_channel_state(mhi_cntrl, mhi_chan, to_state);
>> +		if (ret) {
>> +			mutex_unlock(&mhi_chan->mutex);
>> +			return ret;
>> +		}
>> +		mutex_unlock(&mhi_chan->mutex);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +int mhi_stop_transfer(struct mhi_device *mhi_dev)
>> +{
>> +	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
>> +}
>> +EXPORT_SYMBOL_GPL(mhi_stop_transfer);
>> +
>> +int mhi_start_transfer(struct mhi_device *mhi_dev)
>> +{
>> +	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
>> +}
>> +EXPORT_SYMBOL_GPL(mhi_start_transfer);
>> +
>>   int mhi_poll(struct mhi_device *mhi_dev, u32 budget)
>>   {
>>   	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
>> index aa9757e..35779a0 100644
>> --- a/include/linux/mhi.h
>> +++ b/include/linux/mhi.h
>> @@ -704,6 +704,25 @@ int mhi_prepare_for_transfer(struct mhi_device 
>> *mhi_dev);
>>   void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
>>     /**
>> + * mhi_stop_transfer - Pauses ongoing channel activity by issuing the 
>> STOP
>> + *                     channel command to both UL and DL channels. 
>> This command
>> + *                     does not reset the channel context and the 
>> client drivers
>> + *                     can issue mhi_start_transfer to resume 
>> activity.
>> + * @mhi_dev: Device associated with the channels
>> + */
>> +int mhi_stop_transfer(struct mhi_device *mhi_dev);
>> +
>> +/**
>> + * mhi_start_transfer - Resumes channel activity by issuing the START 
>> channel
>> + *                      command to both UL and DL channels. This 
>> command assumes
>> + *                      the channel context is already setup and the 
>> client
>> + *                      drivers can issue mhi_stop_transfer to pause 
>> activity if
>> + *                      required.
>> + * @mhi_dev: Device associated with the channels
>> + */
>> +int mhi_start_transfer(struct mhi_device *mhi_dev);
>> +
>> +/**
>>    * mhi_poll - Poll for any available data in DL direction
>>    * @mhi_dev: Device associated with the channels
>>    * @budget: # of events to process
>> 
> Overall change looks good.
> 
> Thanks,
> Hemant

Thanks,
Bhaumik
---
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Forum,
a Linux Foundation Collaborative Project