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.
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 (8):
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
drivers/bus/mhi/core/init.c | 22 +++-
drivers/bus/mhi/core/internal.h | 12 ++
drivers/bus/mhi/core/main.c | 238 ++++++++++++++++++++++++++++------------
include/linux/mhi.h | 45 +++++++-
4 files changed, 242 insertions(+), 75 deletions(-)
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
The __mhi_unprepare_channel() API does not require the __ prefix.
Get rid of it and make the internal function consistent with the
other function names.
Signed-off-by: Bhaumik Bhatt <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Reviewed-by: Hemant Kumar <[email protected]>
---
drivers/bus/mhi/core/main.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index f4026af..7d48dfd 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1311,8 +1311,8 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
return -EINVAL;
}
-static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
- struct mhi_chan *mhi_chan)
+static void mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+ struct mhi_chan *mhi_chan)
{
int ret;
struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -1425,7 +1425,7 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
error_pre_alloc:
mutex_unlock(&mhi_chan->mutex);
- __mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+ mhi_unprepare_channel(mhi_cntrl, mhi_chan);
return ret;
}
@@ -1542,7 +1542,7 @@ int mhi_prepare_for_transfer(struct mhi_device *mhi_dev)
if (!mhi_chan)
continue;
- __mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+ mhi_unprepare_channel(mhi_cntrl, mhi_chan);
}
return ret;
@@ -1560,7 +1560,7 @@ void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev)
if (!mhi_chan)
continue;
- __mhi_unprepare_channel(mhi_cntrl, mhi_chan);
+ mhi_unprepare_channel(mhi_cntrl, mhi_chan);
}
}
EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
If a channel was explicitly stopped but not reset, allow it to
move to a disabled state so that the channel context can be
cleaned up after a driver remove is issued. Since the channel
remained in stopped state, its context on the device is not
cleared. Allow this move if a client driver module is unloaded
or a device crash occurs.
Signed-off-by: Bhaumik Bhatt <[email protected]>
Reviewed-by: Hemant Kumar <[email protected]>
---
drivers/bus/mhi/core/init.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index f0697f4..5c93a61 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -1288,7 +1288,8 @@ static int mhi_driver_remove(struct device *dev)
mutex_lock(&mhi_chan->mutex);
- if (ch_state[dir] == MHI_CH_STATE_ENABLED &&
+ if ((ch_state[dir] == MHI_CH_STATE_ENABLED ||
+ ch_state[dir] == MHI_CH_STATE_STOP) &&
!mhi_chan->offload_ch)
mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
Add support to allow sending the STOP channel command. If a
client driver would like to STOP a channel and have the device
retain the channel context instead of issuing a RESET to it and
clearing the context, this would provide support for it after
the ability to send this command is exposed to clients.
Signed-off-by: Bhaumik Bhatt <[email protected]>
---
drivers/bus/mhi/core/main.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 702c31b..a7bb8a7 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1193,6 +1193,11 @@ int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
cmd_tre->dword[0] = MHI_TRE_CMD_RESET_DWORD0;
cmd_tre->dword[1] = MHI_TRE_CMD_RESET_DWORD1(chan);
break;
+ case MHI_CMD_STOP_CHAN:
+ cmd_tre->ptr = MHI_TRE_CMD_STOP_PTR;
+ cmd_tre->dword[0] = MHI_TRE_CMD_STOP_DWORD0;
+ cmd_tre->dword[1] = MHI_TRE_CMD_STOP_DWORD1(chan);
+ break;
case MHI_CMD_START_CHAN:
cmd_tre->ptr = MHI_TRE_CMD_START_PTR;
cmd_tre->dword[0] = MHI_TRE_CMD_START_DWORD0;
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
Improve the channel handling state machine such that all commands
go through a common function and validation process to ensure
that the state machine is not violated in any way and adheres to
the MHI specification.
Signed-off-by: Bhaumik Bhatt <[email protected]>
Reviewed-by: Hemant Kumar <[email protected]>
---
drivers/bus/mhi/core/init.c | 6 ++
drivers/bus/mhi/core/internal.h | 12 +++
drivers/bus/mhi/core/main.c | 166 +++++++++++++++++++++++-----------------
3 files changed, 114 insertions(+), 70 deletions(-)
diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 5c93a61..5cdddb2 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -54,6 +54,12 @@ const char * const mhi_state_str[MHI_STATE_MAX] = {
[MHI_STATE_SYS_ERR] = "SYS_ERR",
};
+const char * const mhi_ch_state_type_str[MHI_CH_STATE_TYPE_MAX] = {
+ [MHI_CH_STATE_TYPE_RESET] = "RESET",
+ [MHI_CH_STATE_TYPE_STOP] = "STOP",
+ [MHI_CH_STATE_TYPE_START] = "START",
+};
+
static const char * const mhi_pm_state_str[] = {
[MHI_PM_STATE_DISABLE] = "DISABLE",
[MHI_PM_STATE_POR] = "POR",
diff --git a/drivers/bus/mhi/core/internal.h b/drivers/bus/mhi/core/internal.h
index 6f80ec3..7e3aac1 100644
--- a/drivers/bus/mhi/core/internal.h
+++ b/drivers/bus/mhi/core/internal.h
@@ -369,6 +369,18 @@ enum mhi_ch_state {
MHI_CH_STATE_ERROR = 0x5,
};
+enum mhi_ch_state_type {
+ MHI_CH_STATE_TYPE_RESET,
+ MHI_CH_STATE_TYPE_STOP,
+ MHI_CH_STATE_TYPE_START,
+ MHI_CH_STATE_TYPE_MAX,
+};
+
+extern const char * const mhi_ch_state_type_str[MHI_CH_STATE_TYPE_MAX];
+#define TO_CH_STATE_TYPE_STR(state) (((state) >= MHI_CH_STATE_TYPE_MAX) ? \
+ "INVALID_STATE" : \
+ mhi_ch_state_type_str[(state)])
+
#define MHI_INVALID_BRSTMODE(mode) (mode != MHI_DB_BRST_DISABLE && \
mode != MHI_DB_BRST_ENABLE)
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index a7bb8a7..4cc5ced 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1219,56 +1219,118 @@ int mhi_send_cmd(struct mhi_controller *mhi_cntrl,
return 0;
}
-static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
- struct mhi_chan *mhi_chan)
+static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
+ struct mhi_chan *mhi_chan,
+ enum mhi_ch_state_type to_state)
{
- int ret;
struct device *dev = &mhi_cntrl->mhi_dev->dev;
+ enum mhi_cmd_type cmd = MHI_CMD_NOP;
+ int ret = -EIO;
+
+ dev_dbg(dev, "Updating channel %s(%d) state to: %s\n", mhi_chan->name,
+ mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+ switch (to_state) {
+ case MHI_CH_STATE_TYPE_RESET:
+ write_lock_irq(&mhi_chan->lock);
+ if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
+ mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
+ mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
+ write_unlock_irq(&mhi_chan->lock);
+ goto exit_invalid_state;
+ }
+ mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
+ write_unlock_irq(&mhi_chan->lock);
- dev_dbg(dev, "Entered: unprepare channel:%d\n", mhi_chan->chan);
+ cmd = MHI_CMD_RESET_CHAN;
+ break;
+ case MHI_CH_STATE_TYPE_STOP:
+ if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
+ goto exit_invalid_state;
- /* no more processing events for this channel */
- mutex_lock(&mhi_chan->mutex);
- write_lock_irq(&mhi_chan->lock);
- if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED &&
- mhi_chan->ch_state != MHI_CH_STATE_SUSPENDED) {
- write_unlock_irq(&mhi_chan->lock);
- mutex_unlock(&mhi_chan->mutex);
- return;
+ cmd = MHI_CMD_STOP_CHAN;
+ break;
+ case MHI_CH_STATE_TYPE_START:
+ if (mhi_chan->ch_state != MHI_CH_STATE_STOP &&
+ mhi_chan->ch_state != MHI_CH_STATE_DISABLED)
+ goto exit_invalid_state;
+
+ cmd = MHI_CMD_START_CHAN;
+ break;
+ default:
+ goto exit_invalid_state;
}
- mhi_chan->ch_state = MHI_CH_STATE_DISABLED;
- write_unlock_irq(&mhi_chan->lock);
+ /* bring host and device out of suspended states */
+ ret = mhi_device_get_sync(mhi_cntrl->mhi_dev);
+ if (ret)
+ return ret;
+ mhi_cntrl->runtime_get(mhi_cntrl);
reinit_completion(&mhi_chan->completion);
- read_lock_bh(&mhi_cntrl->pm_lock);
- if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
- read_unlock_bh(&mhi_cntrl->pm_lock);
- goto error_invalid_state;
+ ret = mhi_send_cmd(mhi_cntrl, mhi_chan, cmd);
+ if (ret) {
+ dev_err(dev, "Failed to send %s(%d) %s command\n",
+ mhi_chan->name, mhi_chan->chan,
+ TO_CH_STATE_TYPE_STR(to_state));
+ goto exit_command_failure;
}
- mhi_cntrl->wake_toggle(mhi_cntrl);
- read_unlock_bh(&mhi_cntrl->pm_lock);
+ ret = wait_for_completion_timeout(&mhi_chan->completion,
+ msecs_to_jiffies(mhi_cntrl->timeout_ms));
+ if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS) {
+ dev_err(dev, "Failed to receive %s(%d) %s command completion\n",
+ mhi_chan->name, mhi_chan->chan,
+ TO_CH_STATE_TYPE_STR(to_state));
+ ret = -EIO;
+ goto exit_command_failure;
+ }
- mhi_cntrl->runtime_get(mhi_cntrl);
+ ret = 0;
+
+ if (to_state != MHI_CH_STATE_TYPE_RESET) {
+ write_lock_irq(&mhi_chan->lock);
+ mhi_chan->ch_state = (to_state == MHI_CH_STATE_TYPE_START) ?
+ MHI_CH_STATE_ENABLED : MHI_CH_STATE_STOP;
+ write_unlock_irq(&mhi_chan->lock);
+ }
+
+ dev_dbg(dev, "Channel %s(%d) state change to %s successful\n",
+ mhi_chan->name, mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+exit_command_failure:
mhi_cntrl->runtime_put(mhi_cntrl);
- ret = mhi_send_cmd(mhi_cntrl, mhi_chan, MHI_CMD_RESET_CHAN);
- if (ret)
- goto error_invalid_state;
+ mhi_device_put(mhi_cntrl->mhi_dev);
- /* even if it fails we will still reset */
- ret = wait_for_completion_timeout(&mhi_chan->completion,
- msecs_to_jiffies(mhi_cntrl->timeout_ms));
- if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS)
- dev_err(dev,
- "Failed to receive cmd completion, still resetting\n");
+ return ret;
+
+exit_invalid_state:
+ dev_err(dev, "Channel %s(%d) update to %s not allowed\n",
+ mhi_chan->name, mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+ return -EINVAL;
+}
+
+static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+ struct mhi_chan *mhi_chan)
+{
+ int ret;
+ struct device *dev = &mhi_cntrl->mhi_dev->dev;
+
+ /* no more processing events for this channel */
+ mutex_lock(&mhi_chan->mutex);
+
+ ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+ MHI_CH_STATE_TYPE_RESET);
+ if (ret)
+ dev_err(dev, "Failed to reset channel, still resetting\n");
-error_invalid_state:
if (!mhi_chan->offload_ch) {
mhi_reset_chan(mhi_cntrl, mhi_chan);
mhi_deinit_chan_ctxt(mhi_cntrl, mhi_chan);
}
- dev_dbg(dev, "chan:%d successfully resetted\n", mhi_chan->chan);
+ dev_dbg(dev, "chan:%d successfully reset\n", mhi_chan->chan);
+
mutex_unlock(&mhi_chan->mutex);
}
@@ -1278,8 +1340,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
int ret = 0;
struct device *dev = &mhi_cntrl->mhi_dev->dev;
- dev_dbg(dev, "Preparing channel: %d\n", mhi_chan->chan);
-
if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
dev_err(dev,
"Current EE: %s Required EE Mask: 0x%x for chan: %s\n",
@@ -1290,14 +1350,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
mutex_lock(&mhi_chan->mutex);
- /* If channel is not in disable state, do not allow it to start */
- if (mhi_chan->ch_state != MHI_CH_STATE_DISABLED) {
- ret = -EIO;
- dev_dbg(dev, "channel: %d is not in disabled state\n",
- mhi_chan->chan);
- goto error_init_chan;
- }
-
/* Check of client manages channel context for offload channels */
if (!mhi_chan->offload_ch) {
ret = mhi_init_chan_ctxt(mhi_cntrl, mhi_chan);
@@ -1305,34 +1357,11 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
goto error_init_chan;
}
- reinit_completion(&mhi_chan->completion);
- read_lock_bh(&mhi_cntrl->pm_lock);
- if (MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)) {
- read_unlock_bh(&mhi_cntrl->pm_lock);
- ret = -EIO;
- goto error_pm_state;
- }
-
- mhi_cntrl->wake_toggle(mhi_cntrl);
- read_unlock_bh(&mhi_cntrl->pm_lock);
- mhi_cntrl->runtime_get(mhi_cntrl);
- mhi_cntrl->runtime_put(mhi_cntrl);
-
- ret = mhi_send_cmd(mhi_cntrl, mhi_chan, MHI_CMD_START_CHAN);
+ ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+ MHI_CH_STATE_TYPE_START);
if (ret)
goto error_pm_state;
- ret = wait_for_completion_timeout(&mhi_chan->completion,
- msecs_to_jiffies(mhi_cntrl->timeout_ms));
- if (!ret || mhi_chan->ccs != MHI_EV_CC_SUCCESS) {
- ret = -EIO;
- goto error_pm_state;
- }
-
- write_lock_irq(&mhi_chan->lock);
- mhi_chan->ch_state = MHI_CH_STATE_ENABLED;
- write_unlock_irq(&mhi_chan->lock);
-
/* Pre-allocate buffer for xfer ring */
if (mhi_chan->pre_alloc) {
int nr_el = get_nr_avail_ring_elements(mhi_cntrl,
@@ -1370,9 +1399,6 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
mutex_unlock(&mhi_chan->mutex);
- dev_dbg(dev, "Chan: %d successfully moved to start state\n",
- mhi_chan->chan);
-
return 0;
error_pm_state:
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
On 12/3/20 5:23 PM, Bhaumik Bhatt wrote:
> Add support to allow sending the STOP channel command. If a
> client driver would like to STOP a channel and have the device
> retain the channel context instead of issuing a RESET to it and
> clearing the context, this would provide support for it after
> the ability to send this command is exposed to clients.
>
> Signed-off-by: Bhaumik Bhatt <[email protected]>
> ---
Reviewed-by: Hemant Kumar <[email protected]>
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project