[PATCH v3 1/4] bus: mhi: core: Add helper API to return number of free TREs

[Hemant Kumar <hemantk@codeaurora.org>]

Introduce mhi_get_no_free_descriptors() API to return number
of TREs available to queue buffer. MHI clients can use this
API to know before hand if ring is full without calling queue
API.

Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 12 ++++++++++++
 include/linux/mhi.h         |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index d25f321..1bd3b1e 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -258,6 +258,18 @@ int mhi_destroy_device(struct device *dev, void *data)
 	return 0;
 }
 
+int mhi_get_no_free_descriptors(struct mhi_device *mhi_dev,
+				enum dma_data_direction dir)
+{
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	struct mhi_chan *mhi_chan = (dir == DMA_TO_DEVICE) ?
+		mhi_dev->ul_chan : mhi_dev->dl_chan;
+	struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
+
+	return get_nr_avail_ring_elements(mhi_cntrl, tre_ring);
+}
+EXPORT_SYMBOL_GPL(mhi_get_no_free_descriptors);
+
 void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason)
 {
 	struct mhi_driver *mhi_drv;
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 6af6bd6..a39b77d 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -602,6 +602,15 @@ void mhi_set_mhi_state(struct mhi_controller *mhi_cntrl,
 void mhi_notify(struct mhi_device *mhi_dev, enum mhi_callback cb_reason);
 
 /**
+ * mhi_get_no_free_descriptors - Get transfer ring length
+ * Get # of TD available to queue buffers
+ * @mhi_dev: Device associated with the channels
+ * @dir: Direction of the channel
+ */
+int mhi_get_no_free_descriptors(struct mhi_device *mhi_dev,
+				enum dma_data_direction dir);
+
+/**
  * mhi_prepare_for_power_up - Do pre-initialization before power up.
  *                            This is optional, call this before power up if
  *                            the controller does not want bus framework to
-- 
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