[v5,8/9] bus: mhi: Improve documentation on channel transfer setup APIs

Commit Message

Bhaumik Bhatt Jan. 8, 2021, 8:54 p.m. UTC

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 <[e-mail]>
Reviewed-by: Hemant Kumar <[e-mail]>
---
 include/linux/mhi.h | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

Patch

diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index b5e11ba..94c5075 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -703,13 +703,35 @@  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);