Re: [PATCH v5 3/9] bus: mhi: core: Improvements to the channel handling state machine

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Jan 08, 2021 at 12:54:51PM -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.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
> ---
>  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 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 c22d7df..081fdf0 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1250,56 +1250,118 @@ 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));

Instead of explicitly using the channel name and its id, you should be
able to use `mhi_chan->mhi_dev->dev` so that dev_dbg() can provide that
information for you. For instance,

mhi0_IPCR: Updating channel state to RESET

Do it for all instances below.

> +
> +	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);

You are sneaking in a change here. Please add it to the commit description.

> +	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;
> +

This is not a recommended way to handle error paths. There should be a
single return for all error paths. Please fix it.

> +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 */

Move this comment below.

Thanks,
Mani