[PATCH v7 0/7] Updates to MHI channel handling

[PATCH v7 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 and x86_64 architecture.

v7:
-Tested on x86_64 architecture
-Drop the patch "Do not clear channel context more than once" as issue is fixed
differently using "bus: mhi: core: Fix double dma free()"
-Update the commit text to better reflect changes on state machine improvements

v6:
-Dropped the patch which introduced start/stop transfer APIs for lack of users
-Updated error handling and debug prints on channel handling improvements patch
-Improved commit text to better explain certain patches based on review comments
-Removed references to new APIs from the documentation improvement patch

v5:
-Added reviewed-by tags from Hemant I missed earlier
-Added patch to prevent kernel warnings on clearing channel context twice

v4:
-Updated commit text/descriptions and addressed checkpatch checks
-Added context validity check before starting/stopping channels from new API
-Added patch to clear channel context configuration after reset/unprepare

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 sending the STOP channel command
  bus: mhi: core: Clear context for stopped channels from remove()
  bus: mhi: core: Improvements to the channel handling state machine
  bus: mhi: core: Clear configuration from channel context during reset
  bus: mhi: core: Check channel execution environment 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     |  22 ++++-
 drivers/bus/mhi/core/internal.h |  12 +++
 drivers/bus/mhi/core/main.c     | 192 ++++++++++++++++++++++++----------------
 include/linux/mhi.h             |  18 +++-
 4 files changed, 163 insertions(+), 81 deletions(-)

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

[PATCH v7 1/7] bus: mhi: core: Allow sending the STOP channel command

[Bhaumik Bhatt]

Add support to allow sending the STOP channel command. If a
client driver would like to STOP a channel and have the device
retain the channel context instead of issuing a RESET to it and
clearing the context, this would provide support for it after
the ability to send this command is exposed to clients.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.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 d377d07..0dc3749 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1182,6 +1182,11 @@ 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 v7 2/7] bus: mhi: core: Clear context for stopped channels from remove()

[Bhaumik Bhatt]

If a channel was explicitly stopped but not reset and a driver
remove is issued, clean up the channel context such that it is
reflected on the device. This move is useful if a client driver
module is unloaded or a device crash occurs with the host having
placed the channel in a stopped state.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.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 706484f..bd62efcb 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -1291,7 +1291,8 @@ 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 v7 3/7] bus: mhi: core: Improvements to the channel handling state machine

[Bhaumik Bhatt]

Improve the channel handling state machine such that all commands
go through a common function and a validation process to ensure
that the state machine is not violated in any way and adheres to
the MHI specification. Using this common function allows MHI to:
1. Fail early if device is in a bad state by attempting to assert
device wake before sending a channel update command instead of
performing a wake toggle and waiting longer for the send to fail
2. Use channel specific print messages to accurately identify the
use client device for the channel(s) being updated
3. Eliminate unnecessary debug messages and code duplication

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
---
 drivers/bus/mhi/core/init.c     |   6 ++
 drivers/bus/mhi/core/internal.h |  12 +++
 drivers/bus/mhi/core/main.c     | 172 ++++++++++++++++++++++------------------
 3 files changed, 114 insertions(+), 76 deletions(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index bd62efcb..64846c4 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 6f37439..d8fd197 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 0dc3749..6c3234e 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1208,56 +1208,114 @@ 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;
+	struct device *dev = &mhi_chan->mhi_dev->dev;
+	enum mhi_cmd_type cmd = MHI_CMD_NOP;
+	int ret = -EIO;
+
+	dev_dbg(dev, "%d: Updating channel state to: %s\n", 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);
+			return -EINVAL;
+		}
+		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)
+			return -EINVAL;
 
-	/* 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)
+			return -EINVAL;
+
+		cmd = MHI_CMD_START_CHAN;
+		break;
+	default:
+		dev_err(dev, "%d: Channel state update to %s not allowed\n",
+			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+		return -EINVAL;
 	}
 
-	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, "%d: Failed to send %s channel command\n",
+			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+		goto exit_channel_update;
 	}
 
-	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,
+			"%d: Failed to receive %s channel command completion\n",
+			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+		ret = -EIO;
+		goto exit_channel_update;
+	}
 
-	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, "%d: Channel state change to %s successful\n",
+		mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+exit_channel_update:
 	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;
+}
+
+static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+				    struct mhi_chan *mhi_chan)
+{
+	int ret;
+	struct device *dev = &mhi_chan->mhi_dev->dev;
+
+	mutex_lock(&mhi_chan->mutex);
+
+	/* no more processing events for this channel */
+	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+				       MHI_CH_STATE_TYPE_RESET);
+	if (ret)
+		dev_err(dev, "%d: Failed to reset channel, still resetting\n",
+			mhi_chan->chan);
 
-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, "%d: successfully reset\n", mhi_chan->chan);
+
 	mutex_unlock(&mhi_chan->mutex);
 }
 
@@ -1265,28 +1323,16 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
 			struct mhi_chan *mhi_chan)
 {
 	int ret = 0;
-	struct device *dev = &mhi_cntrl->mhi_dev->dev;
-
-	dev_dbg(dev, "Preparing channel: %d\n", mhi_chan->chan);
+	struct device *dev = &mhi_chan->mhi_dev->dev;
 
 	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);
+		dev_err(dev, "Current EE: %s Required EE Mask: 0x%x\n",
+			TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
 		return -ENOTCONN;
 	}
 
 	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);
@@ -1294,34 +1340,11 @@ 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,
@@ -1359,9 +1382,6 @@ 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 v7 4/7] bus: mhi: core: Clear configuration from channel context during reset

[Bhaumik Bhatt]

When clearing up the channel context after client drivers are
done using channels, the configuration is currently not being
reset entirely. Ensure this is done to appropriately handle
issues where clients unaware of the context state end up calling
functions which expect a context.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/core/init.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 64846c4..8b840da 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -556,6 +556,7 @@ void mhi_deinit_chan_ctxt(struct mhi_controller *mhi_cntrl,
 	struct mhi_ring *buf_ring;
 	struct mhi_ring *tre_ring;
 	struct mhi_chan_ctxt *chan_ctxt;
+	u32 tmp;
 
 	buf_ring = &mhi_chan->buf_ring;
 	tre_ring = &mhi_chan->tre_ring;
@@ -569,7 +570,19 @@ void mhi_deinit_chan_ctxt(struct mhi_controller *mhi_cntrl,
 	vfree(buf_ring->base);
 
 	buf_ring->base = tre_ring->base = NULL;
+	tre_ring->ctxt_wp = NULL;
 	chan_ctxt->rbase = 0;
+	chan_ctxt->rlen = 0;
+	chan_ctxt->rp = 0;
+	chan_ctxt->wp = 0;
+
+	tmp = chan_ctxt->chcfg;
+	tmp &= ~CHAN_CTX_CHSTATE_MASK;
+	tmp |= (MHI_CH_STATE_DISABLED << CHAN_CTX_CHSTATE_SHIFT);
+	chan_ctxt->chcfg = tmp;
+
+	/* Update to all cores */
+	smp_wmb();
 }
 
 int mhi_init_chan_ctxt(struct mhi_controller *mhi_cntrl,
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v7 5/7] bus: mhi: core: Check channel execution environment 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 as the device will no longer be able
to respond to such a request.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/bus/mhi/core/main.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 6c3234e..f34f8f6 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1303,6 +1303,12 @@ static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
 
 	mutex_lock(&mhi_chan->mutex);
 
+	if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
+		dev_dbg(dev, "Current EE: %s Required EE Mask: 0x%x\n",
+			TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
+		goto exit_unprepare_channel;
+	}
+
 	/* no more processing events for this channel */
 	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
 				       MHI_CH_STATE_TYPE_RESET);
@@ -1310,6 +1316,11 @@ static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
 		dev_err(dev, "%d: Failed to reset channel, still resetting\n",
 			mhi_chan->chan);
 
+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 v7 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>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.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 f34f8f6..5bb1785 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1295,8 +1295,8 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
 	return ret;
 }
 
-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_chan->mhi_dev->dev;
@@ -1406,7 +1406,7 @@ 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;
 }
@@ -1523,7 +1523,7 @@ 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;
@@ -1541,7 +1541,7 @@ 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 v7 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. Add details on what MHI does
when these APIs are used.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 include/linux/mhi.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 8f5bf40..838a3c4 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -712,13 +712,27 @@ 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.
  * @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.
  * @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 v7 3/7] bus: mhi: core: Improvements to the channel handling state machine

[Manivannan Sadhasivam]

On Mon, Mar 29, 2021 at 07:11:43PM -0700, Bhaumik Bhatt wrote:
> Improve the channel handling state machine such that all commands
> go through a common function and a validation process to ensure
> that the state machine is not violated in any way and adheres to
> the MHI specification. Using this common function allows MHI to:
> 1. Fail early if device is in a bad state by attempting to assert
> device wake before sending a channel update command instead of
> performing a wake toggle and waiting longer for the send to fail
> 2. Use channel specific print messages to accurately identify the
> use client device for the channel(s) being updated
> 3. Eliminate unnecessary debug messages and code duplication

Please don't club these changes in a single patch. Split them as
individual patches.

Thanks,
Mani

> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
> ---
>  drivers/bus/mhi/core/init.c     |   6 ++
>  drivers/bus/mhi/core/internal.h |  12 +++
>  drivers/bus/mhi/core/main.c     | 172 ++++++++++++++++++++++------------------
>  3 files changed, 114 insertions(+), 76 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index bd62efcb..64846c4 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 6f37439..d8fd197 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 0dc3749..6c3234e 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1208,56 +1208,114 @@ 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;
> +	struct device *dev = &mhi_chan->mhi_dev->dev;
> +	enum mhi_cmd_type cmd = MHI_CMD_NOP;
> +	int ret = -EIO;
> +
> +	dev_dbg(dev, "%d: Updating channel state to: %s\n", 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);
> +			return -EINVAL;
> +		}
> +		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)
> +			return -EINVAL;
>  
> -	/* 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)
> +			return -EINVAL;
> +
> +		cmd = MHI_CMD_START_CHAN;
> +		break;
> +	default:
> +		dev_err(dev, "%d: Channel state update to %s not allowed\n",
> +			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> +		return -EINVAL;
>  	}
>  
> -	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, "%d: Failed to send %s channel command\n",
> +			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> +		goto exit_channel_update;
>  	}
>  
> -	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,
> +			"%d: Failed to receive %s channel command completion\n",
> +			mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> +		ret = -EIO;
> +		goto exit_channel_update;
> +	}
>  
> -	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, "%d: Channel state change to %s successful\n",
> +		mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
> +
> +exit_channel_update:
>  	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;
> +}
> +
> +static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
> +				    struct mhi_chan *mhi_chan)
> +{
> +	int ret;
> +	struct device *dev = &mhi_chan->mhi_dev->dev;
> +
> +	mutex_lock(&mhi_chan->mutex);
> +
> +	/* no more processing events for this channel */
> +	ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
> +				       MHI_CH_STATE_TYPE_RESET);
> +	if (ret)
> +		dev_err(dev, "%d: Failed to reset channel, still resetting\n",
> +			mhi_chan->chan);
>  
> -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, "%d: successfully reset\n", mhi_chan->chan);
> +
>  	mutex_unlock(&mhi_chan->mutex);
>  }
>  
> @@ -1265,28 +1323,16 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
>  			struct mhi_chan *mhi_chan)
>  {
>  	int ret = 0;
> -	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> -
> -	dev_dbg(dev, "Preparing channel: %d\n", mhi_chan->chan);
> +	struct device *dev = &mhi_chan->mhi_dev->dev;
>  
>  	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);
> +		dev_err(dev, "Current EE: %s Required EE Mask: 0x%x\n",
> +			TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
>  		return -ENOTCONN;
>  	}
>  
>  	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);
> @@ -1294,34 +1340,11 @@ 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,
> @@ -1359,9 +1382,6 @@ 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
> 

Re: [PATCH v7 0/7] Updates to MHI channel handling

[Manivannan Sadhasivam]

On Mon, Mar 29, 2021 at 07:11:40PM -0700, Bhaumik Bhatt wrote:
> 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 and x86_64 architecture.
> 

Please rebase this series on top of mhi-next as some of the patches
doesn't apply cleanly.

Thanks,
Mani

> v7:
> -Tested on x86_64 architecture
> -Drop the patch "Do not clear channel context more than once" as issue is fixed
> differently using "bus: mhi: core: Fix double dma free()"
> -Update the commit text to better reflect changes on state machine improvements
> 
> v6:
> -Dropped the patch which introduced start/stop transfer APIs for lack of users
> -Updated error handling and debug prints on channel handling improvements patch
> -Improved commit text to better explain certain patches based on review comments
> -Removed references to new APIs from the documentation improvement patch
> 
> v5:
> -Added reviewed-by tags from Hemant I missed earlier
> -Added patch to prevent kernel warnings on clearing channel context twice
> 
> v4:
> -Updated commit text/descriptions and addressed checkpatch checks
> -Added context validity check before starting/stopping channels from new API
> -Added patch to clear channel context configuration after reset/unprepare
> 
> 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 sending the STOP channel command
>   bus: mhi: core: Clear context for stopped channels from remove()
>   bus: mhi: core: Improvements to the channel handling state machine
>   bus: mhi: core: Clear configuration from channel context during reset
>   bus: mhi: core: Check channel execution environment 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     |  22 ++++-
>  drivers/bus/mhi/core/internal.h |  12 +++
>  drivers/bus/mhi/core/main.c     | 192 ++++++++++++++++++++++++----------------
>  include/linux/mhi.h             |  18 +++-
>  4 files changed, 163 insertions(+), 81 deletions(-)
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>