Date:   Wed, 24 Feb 2021 17:39:45 -0800
From:   Bhaumik Bhatt <bbhatt@...eaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org,
        loic.poulain@...aro.org
Subject: Re: [PATCH v6 3/8] bus: mhi: core: Improvements to the channel
 handling state machine

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@...eaurora.org>
>> Reviewed-by: Hemant Kumar <hemantk@...eaurora.org>
>> ---
>>  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:
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> 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

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