Re: [PATCH v7 3/7] bus: mhi: core: Improvements to the channel handling state machine

[Manivannan Sadhasivam]

On Mon, Mar 29, 2021 at 07:11:43PM -0700, Bhaumik Bhatt wrote:
> Improve the channel handling state machine such that all commands
> go through a common function and a validation process to ensure
> that the state machine is not violated in any way and adheres to
> the MHI specification. Using this common function allows MHI to:
> 1. Fail early if device is in a bad state by attempting to assert
> device wake before sending a channel update command instead of
> performing a wake toggle and waiting longer for the send to fail
> 2. Use channel specific print messages to accurately identify the
> use client device for the channel(s) being updated
> 3. Eliminate unnecessary debug messages and code duplication

Please don't club these changes in a single patch. Split them as
individual patches.

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 bd62efcb..64846c4 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 6f37439..d8fd197 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 0dc3749..6c3234e 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1208,56 +1208,114 @@ 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);
>  }
>  
> @@ -1265,28 +1323,16 @@ 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);
> @@ -1294,34 +1340,11 @@ 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,
> @@ -1359,9 +1382,6 @@ 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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