[PATCH v1 3/4] bus: mhi: core: Add support to pause or resume channel data transfers

[Bhaumik Bhatt <bbhatt@codeaurora.org>]

Some MHI clients may want to request for pausing or resuming of the
data transfers for their channels. Enable them to do so using the new
APIs provided for the same.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/mhi.h         | 16 ++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 1226933..01845c6 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1560,6 +1560,47 @@ 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_pause_transfer(struct mhi_device *mhi_dev)
+{
+	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
+}
+EXPORT_SYMBOL_GPL(mhi_pause_transfer);
+
+int mhi_resume_transfer(struct mhi_device *mhi_dev)
+{
+	return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
+}
+EXPORT_SYMBOL_GPL(mhi_resume_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 52b3c60..4d48d49 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -702,6 +702,22 @@ int mhi_prepare_for_transfer(struct mhi_device *mhi_dev);
 void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
 
 /**
+ * mhi_pause_transfer - Pause ongoing channel activity
+ * Moves both UL and DL channels to STOP state to halt
+ * pending transfers.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_pause_transfer(struct mhi_device *mhi_dev);
+
+/**
+ * mhi_resume_transfer - Resume channel activity
+ * Moves both UL and DL channels to START state to
+ * resume transfers.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_resume_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
-- 
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