Re: [PATCH v6 3/8] bus: mhi: core: Improvements to the channel handling state machine

From: Bhaumik Bhatt
Date: Wed Feb 24 2021 - 20:40:46 EST

Hi Mani,

On 2021-02-24 02:03 AM, Manivannan Sadhasivam wrote:
On Thu, Feb 04, 2021 at 12:28:01PM -0800, Bhaumik Bhatt wrote:
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. Assert device wake before sending the
channel update commands instead of a wake toggle to ensure we
fail if device is in a bad state. Also update print messages to
use client device to accurately represent the channel being
updated.


This patch is doing atleast 3 things and that is not acceptable. Please
split this patch and send.

These changes to commit text and other updates were done after your comments for v5
[1].

Please check and let me know what you think. I have addressed them and added info
in the commit description.

I feel this is one patch to improve channel handling overall, so the "assert device wake"
change is part of that and I have stated that.

Thanks,
Mani

Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
Reviewed-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
---
drivers/bus/mhi/core/init.c | 6 ++
drivers/bus/mhi/core/internal.h | 12 +++
drivers/bus/mhi/core/main.c | 172 ++++++++++++++++++++++------------------
3 files changed, 114 insertions(+), 76 deletions(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 03c5786..482b365 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 d068188..2f6fdb2 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -1188,56 +1188,114 @@ 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;
+ struct device *dev = &mhi_chan->mhi_dev->dev;
+ enum mhi_cmd_type cmd = MHI_CMD_NOP;
+ int ret = -EIO;
+
+ dev_dbg(dev, "%d: Updating channel state to: %s\n", 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);
+ return -EINVAL;
+ }
+ 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)
+ return -EINVAL;

- /* 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)
+ return -EINVAL;
+
+ cmd = MHI_CMD_START_CHAN;
+ break;
+ default:
+ dev_err(dev, "%d: Channel state update to %s not allowed\n",
+ mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+ return -EINVAL;
}

- 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, "%d: Failed to send %s channel command\n",
+ mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+ goto exit_channel_update;
}

- 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,
+ "%d: Failed to receive %s channel command completion\n",
+ mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+ ret = -EIO;
+ goto exit_channel_update;
+ }

- 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, "%d: Channel state change to %s successful\n",
+ mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
+
+exit_channel_update:
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;
+}
+
+static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
+ struct mhi_chan *mhi_chan)
+{
+ int ret;
+ struct device *dev = &mhi_chan->mhi_dev->dev;
+
+ mutex_lock(&mhi_chan->mutex);
+
+ /* no more processing events for this channel */
+ ret = mhi_update_channel_state(mhi_cntrl, mhi_chan,
+ MHI_CH_STATE_TYPE_RESET);
+ if (ret)
+ dev_err(dev, "%d: Failed to reset channel, still resetting\n",
+ mhi_chan->chan);

-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, "%d: successfully reset\n", mhi_chan->chan);
+
mutex_unlock(&mhi_chan->mutex);
}

@@ -1245,28 +1303,16 @@ int mhi_prepare_channel(struct mhi_controller *mhi_cntrl,
struct mhi_chan *mhi_chan)
{
int ret = 0;
- struct device *dev = &mhi_cntrl->mhi_dev->dev;
-
- dev_dbg(dev, "Preparing channel: %d\n", mhi_chan->chan);
+ struct device *dev = &mhi_chan->mhi_dev->dev;

if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
- dev_err(dev,
- "Current EE: %s Required EE Mask: 0x%x for chan: %s\n",
- TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask,
- mhi_chan->name);
+ dev_err(dev, "Current EE: %s Required EE Mask: 0x%x\n",
+ TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask);
return -ENOTCONN;
}

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);
@@ -1274,34 +1320,11 @@ 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,
@@ -1339,9 +1362,6 @@ 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:
--
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a Linux Foundation Collaborative Project


[1] https://lkml.org/lkml/2021/1/21/781

Thanks,
Bhaumik
---
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project