Hi Mani,
On 2020-11-16 04:43, Manivannan Sadhasivam wrote:
On Wed, Nov 11, 2020 at 11:21:10AM -0800, Bhaumik Bhatt wrote:
Some MHI client drivers may want to request a pause or halt of
data transfer activity on their channels. Support for this does
not exist and must be introduced, wherein the channel context is
not reset or cleared but only the STOP channel command is issued.
This would need to be paired with an API that allows resuming the
data transfer activity on channels by use of the START channel
command. This API assumes that the context information is already
setup. Enable this using two new APIs, mhi_start_transfer() and
mhi_stop_transfer().
Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
---
drivers/bus/mhi/core/main.c | 41
+++++++++++++++++++++++++++++++++++++++++
include/linux/mhi.h | 19 +++++++++++++++++++
2 files changed, 60 insertions(+)
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 1226933..1a969f4 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);
Hmm. The documentation about wait_for_completion*() used in
mhi_update_channel_state()says below,
"As all variants of wait_for_completion() can (obviously) block for a
long
time depending on the nature of the activity they are waiting for, so
in
most cases you probably don't want to call this with held mutexes."
Yes, that is understood. The mhi_chan->mutex is only used to lock any
channel
enable/start/stop/disable type operations, since these have to be in
order, it
is essential that we wait for one of the operations to finish before the
next
one.
Also we avoid a race, for example, at a time when a device crash forces
a driver
"remove" call, while an operation to start/stop a channel is already
going on.
+ 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_stop_transfer(struct mhi_device *mhi_dev)
+{
+ return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
+}
+EXPORT_SYMBOL_GPL(mhi_stop_transfer);
+
+int mhi_start_transfer(struct mhi_device *mhi_dev)
+{
+ return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
+}
+EXPORT_SYMBOL_GPL(mhi_start_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..aee8494 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -702,6 +702,25 @@ int mhi_prepare_for_transfer(struct mhi_device
*mhi_dev);
void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
/**
+ * mhi_stop_transfer - Pauses ongoing channel activity by issuing the
STOP
+ * channel command to both UL and DL channels.
This command
+ * does not reset the channel context and the
client drivers
+ * can issue mhi_start_transfer to resume
activity.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_stop_transfer(struct mhi_device *mhi_dev);
+
+/**
+ * mhi_start_transfer - Resumes channel activity by issuing the START
channel
+ * command to both UL and DL channels. This
command assumes
+ * the channel context is already setup and the
client
+ * drivers can issue mhi_stop_transfer to pause
activity if
+ * required.
+ * @mhi_dev: Device associated with the channels
+ */
+int mhi_start_transfer(struct mhi_device *mhi_dev);
+
+/**
Align the comment header properly.
So I am trying to follow the documentation style for other functions in
the same
file. Is there any particular format you want me to refer to?
I use all spaces for the lines after the first one to align them just
like the
rest of them.
Thanks,
Mani
* mhi_poll - Poll for any available data in DL direction
* @mhi_dev: Device associated with the channels
* @budget: # of events to process
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
Thanks,
Bhaumik
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
