linux-kernel - [PATCH v4 8/8] bus: mhi: Improve documentation on channel transfer setup APIs

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Date:   Thu,  3 Dec 2020 17:23:17 -0800
From:   Bhaumik Bhatt <bbhatt@...eaurora.org>
To:     manivannan.sadhasivam@...aro.org, hemantk@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org, loic.poulain@...aro.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org,
        Bhaumik Bhatt <bbhatt@...eaurora.org>
Subject: [PATCH v4 8/8] bus: mhi: Improve documentation on channel transfer setup APIs

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@...eaurora.org>
Reviewed-by: Hemant Kumar <hemantk@...eaurora.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);
-- 
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