MHI specification shows a state machine with support for STOP channel command
and the validity of certain state transitions. MHI host currently does not
provide any mechanism to stop a channel and restart it without resetting it.
There are also times when the device moves on to a different execution
environment while client drivers on the host are unaware of it and still
attempt to reset the channels facing unnecessary timeouts.
This series addresses the above areas to provide support for stopping an MHI
channel, resuming it back, improved documentation and improving upon channel
state machine handling in general.
This set of patches was tested on arm64 architecture.
v5:
-Added reviewed-by tags from Hemant I missed earlier
-Added patch to prevent kernel warnings on clearing channel context twice
v4:
-Updated commit text/descriptions and addressed checkpatch checks
-Added context validity check before starting/stopping channels from new API
-Added patch to clear channel context configuration after reset/unprepare
v3:
-Updated documentation for channel transfer APIs to highlight differences
-Create separate patch for "allowing channel to be disabled from stopped state"
v2:
-Renamed the newly introduced APIs to mhi_start_transfer() / mhi_stop_transfer()
-Added improved documentation to avoid confusion with the new APIs
-Removed the __ prefix from mhi_unprepare_channel() API for consistency.
Bhaumik Bhatt (9):
bus: mhi: core: Allow sending the STOP channel command
bus: mhi: core: Allow channel to be disabled from stopped state
bus: mhi: core: Improvements to the channel handling state machine
bus: mhi: core: Clear configuration from channel context during reset
bus: mhi: core: Add support to stop or start channel data transfers
bus: mhi: core: Check channel execution environment before issuing
reset
bus: mhi: core: Remove __ prefix for MHI channel unprepare function
bus: mhi: Improve documentation on channel transfer setup APIs
bus: mhi: core: Do not clear channel context more than once
drivers/bus/mhi/core/init.c | 23 +++-
drivers/bus/mhi/core/internal.h | 12 ++
drivers/bus/mhi/core/main.c | 238 ++++++++++++++++++++++++++++------------
include/linux/mhi.h | 45 +++++++-
4 files changed, 243 insertions(+), 75 deletions(-)
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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 <[email protected]>
Reviewed-by: Hemant Kumar <[email protected]>
---
drivers/bus/mhi/core/main.c | 50 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/mhi.h | 19 +++++++++++++++++
2 files changed, 69 insertions(+)
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 081fdf0..a84e6aa 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1583,6 +1583,56 @@ 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 device *dev = &mhi_cntrl->mhi_dev->dev;
+ struct mhi_chan *mhi_chan;
+ struct mhi_chan_ctxt *chan_ctxt;
+ 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 fails as client will reset
+ * both upon failure
+ */
+ mutex_lock(&mhi_chan->mutex);
+ chan_ctxt = &mhi_cntrl->mhi_ctxt->chan_ctxt[mhi_chan->chan];
+ if (!(chan_ctxt->chcfg & CHAN_CTX_CHSTATE_MASK)) {
+ mutex_unlock(&mhi_chan->mutex);
+ dev_err(dev, "Channel %s(%u) context not initialized\n",
+ mhi_chan->name, mhi_chan->chan);
+ return -EINVAL;
+ }
+ 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 fe65554..b5e11ba 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -715,6 +715,25 @@ 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);
+
+/**
* 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