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Date:   Sat, 31 Oct 2020 12:24:09 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     bbhatt@...eaurora.org, Bhaumik Bhatt <bbhatt@...eaurora.org>
CC:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 10/12] bus: mhi: core: Separate system error and power down handling

Hi Bhaumik, 

On 31 October 2020 1:04:07 AM IST, Bhaumik Bhatt <bbhatt@...eaurora.org> wrote:
>Hi Mani,
>
>On 2020-10-30 07:06, Manivannan Sadhasivam wrote:
>> On Thu, Oct 29, 2020 at 09:10:55PM -0700, Bhaumik Bhatt wrote:
>>> Currently, there exist a set of if...else statements in the
>>> mhi_pm_disable_transition() function which make handling system
>>> error and disable transitions differently complex. To make that
>>> cleaner and facilitate differences in behavior, separate these
>>> two transitions for MHI host.
>>> 
>> 
>> And this results in a lot of duplicated code :/
>> 
>> Thanks,
>> Mani
>> 
>
>I knew this was coming. Mainly, we can avoid adding confusing if...else
>statements that plague the current mhi_pm_disable_transition() function
>
>and in
>return for some duplicate code, we can make handling separate use cases
>
>easier
>as they could pop-up anytime in the future.
>

If that happens then do it but now, please no. 

Thanks, 
Mani

>>> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
>>> ---
>>>  drivers/bus/mhi/core/pm.c | 159 
>>> +++++++++++++++++++++++++++++++++++++++-------
>>>  1 file changed, 137 insertions(+), 22 deletions(-)
>>> 
>>> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
>>> index 1d04e401..347ae7d 100644
>>> --- a/drivers/bus/mhi/core/pm.c
>>> +++ b/drivers/bus/mhi/core/pm.c
>>> @@ -444,7 +444,7 @@ static int mhi_pm_mission_mode_transition(struct
>
>>> mhi_controller *mhi_cntrl)
>>>  	return ret;
>>>  }
>>> 
>>> -/* Handle SYS_ERR and Shutdown transitions */
>>> +/* Handle shutdown transitions */
>>>  static void mhi_pm_disable_transition(struct mhi_controller 
>>> *mhi_cntrl,
>>>  				      enum mhi_pm_state transition_state)
>>>  {
>>> @@ -460,10 +460,6 @@ static void mhi_pm_disable_transition(struct 
>>> mhi_controller *mhi_cntrl,
>>>  		to_mhi_pm_state_str(mhi_cntrl->pm_state),
>>>  		to_mhi_pm_state_str(transition_state));
>>> 
>>> -	/* We must notify MHI control driver so it can clean up first */
>>> -	if (transition_state == MHI_PM_SYS_ERR_PROCESS)
>>> -		mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_SYS_ERROR);
>>> -
>>>  	mutex_lock(&mhi_cntrl->pm_mutex);
>>>  	write_lock_irq(&mhi_cntrl->pm_lock);
>>>  	prev_state = mhi_cntrl->pm_state;
>>> @@ -502,11 +498,8 @@ static void mhi_pm_disable_transition(struct 
>>> mhi_controller *mhi_cntrl,
>>>  							    MHICTRL_RESET_SHIFT,
>>>  							    &in_reset) ||
>>>  					!in_reset, timeout);
>>> -		if ((!ret || in_reset) && cur_state == MHI_PM_SYS_ERR_PROCESS) {
>>> +		if (!ret || in_reset)
>>>  			dev_err(dev, "Device failed to exit MHI Reset state\n");
>>> -			mutex_unlock(&mhi_cntrl->pm_mutex);
>>> -			return;
>>> -		}
>>> 
>>>  		/*
>>>  		 * Device will clear BHI_INTVEC as a part of RESET processing,
>>> @@ -566,19 +559,142 @@ static void mhi_pm_disable_transition(struct 
>>> mhi_controller *mhi_cntrl,
>>>  		er_ctxt->wp = er_ctxt->rbase;
>>>  	}
>>> 
>>> -	if (cur_state == MHI_PM_SYS_ERR_PROCESS) {
>>> -		mhi_ready_state_transition(mhi_cntrl);
>>> -	} else {
>>> -		/* Move to disable state */
>>> -		write_lock_irq(&mhi_cntrl->pm_lock);
>>> -		cur_state = mhi_tryset_pm_state(mhi_cntrl, MHI_PM_DISABLE);
>>> -		write_unlock_irq(&mhi_cntrl->pm_lock);
>>> -		if (unlikely(cur_state != MHI_PM_DISABLE))
>>> -			dev_err(dev, "Error moving from PM state: %s to: %s\n",
>>> -				to_mhi_pm_state_str(cur_state),
>>> -				to_mhi_pm_state_str(MHI_PM_DISABLE));
>>> +	/* Move to disable state */
>>> +	write_lock_irq(&mhi_cntrl->pm_lock);
>>> +	cur_state = mhi_tryset_pm_state(mhi_cntrl, MHI_PM_DISABLE);
>>> +	write_unlock_irq(&mhi_cntrl->pm_lock);
>>> +	if (unlikely(cur_state != MHI_PM_DISABLE))
>>> +		dev_err(dev, "Error moving from PM state: %s to: %s\n",
>>> +			to_mhi_pm_state_str(cur_state),
>>> +			to_mhi_pm_state_str(MHI_PM_DISABLE));
>>> +
>>> +	dev_dbg(dev, "Exiting with PM state: %s, MHI state: %s\n",
>>> +		to_mhi_pm_state_str(mhi_cntrl->pm_state),
>>> +		TO_MHI_STATE_STR(mhi_cntrl->dev_state));
>>> +
>>> +	mutex_unlock(&mhi_cntrl->pm_mutex);
>>> +}
>>> +
>>> +/* Handle system error transitions */
>>> +static void mhi_pm_sys_error_transition(struct mhi_controller 
>>> *mhi_cntrl)
>>> +{
>>> +	enum mhi_pm_state cur_state, prev_state;
>>> +	struct mhi_event *mhi_event;
>>> +	struct mhi_cmd_ctxt *cmd_ctxt;
>>> +	struct mhi_cmd *mhi_cmd;
>>> +	struct mhi_event_ctxt *er_ctxt;
>>> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>>> +	int ret, i;
>>> +
>>> +	dev_dbg(dev, "Transitioning from PM state: %s to: %s\n",
>>> +		to_mhi_pm_state_str(mhi_cntrl->pm_state),
>>> +		to_mhi_pm_state_str(MHI_PM_SYS_ERR_PROCESS));
>>> +
>>> +	/* We must notify MHI control driver so it can clean up first */
>>> +	mhi_cntrl->status_cb(mhi_cntrl, MHI_CB_SYS_ERROR);
>>> +
>>> +	mutex_lock(&mhi_cntrl->pm_mutex);
>>> +	write_lock_irq(&mhi_cntrl->pm_lock);
>>> +	prev_state = mhi_cntrl->pm_state;
>>> +	cur_state = mhi_tryset_pm_state(mhi_cntrl,
>MHI_PM_SYS_ERR_PROCESS);
>>> +	write_unlock_irq(&mhi_cntrl->pm_lock);
>>> +
>>> +	if (cur_state != MHI_PM_SYS_ERR_PROCESS) {
>>> +		dev_err(dev, "Failed to transition from PM state: %s to: %s\n",
>>> +			to_mhi_pm_state_str(cur_state),
>>> +			to_mhi_pm_state_str(MHI_PM_SYS_ERR_PROCESS));
>>> +		goto exit_sys_error_transition;
>>> +	}
>>> +
>>> +	mhi_cntrl->ee = MHI_EE_DISABLE_TRANSITION;
>>> +	mhi_cntrl->dev_state = MHI_STATE_RESET;
>>> +
>>> +	/* Wake up threads waiting for state transition */
>>> +	wake_up_all(&mhi_cntrl->state_event);
>>> +
>>> +	/* Trigger MHI RESET so that the device will not access host
>memory 
>>> */
>>> +	if (MHI_REG_ACCESS_VALID(prev_state)) {
>>> +		u32 in_reset = -1;
>>> +		unsigned long timeout = msecs_to_jiffies(mhi_cntrl->timeout_ms);
>>> +
>>> +		dev_dbg(dev, "Triggering MHI Reset in device\n");
>>> +		mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
>>> +
>>> +		/* Wait for the reset bit to be cleared by the device */
>>> +		ret = wait_event_timeout(mhi_cntrl->state_event,
>>> +					 mhi_read_reg_field(mhi_cntrl,
>>> +							    mhi_cntrl->regs,
>>> +							    MHICTRL,
>>> +							    MHICTRL_RESET_MASK,
>>> +							    MHICTRL_RESET_SHIFT,
>>> +							    &in_reset) ||
>>> +					!in_reset, timeout);
>>> +		if (!ret || in_reset) {
>>> +			dev_err(dev, "Device failed to exit MHI Reset state\n");
>>> +			goto exit_sys_error_transition;
>>> +		}
>>> +
>>> +		/*
>>> +		 * Device will clear BHI_INTVEC as a part of RESET processing,
>>> +		 * hence re-program it
>>> +		 */
>>> +		mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
>>> +	}
>>> +
>>> +	dev_dbg(dev,
>>> +		"Waiting for all pending event ring processing to complete\n");
>>> +	mhi_event = mhi_cntrl->mhi_event;
>>> +	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, mhi_event++) {
>>> +		if (mhi_event->offload_ev)
>>> +			continue;
>>> +		tasklet_kill(&mhi_event->task);
>>>  	}
>>> 
>>> +	/* Release lock and wait for all pending threads to complete */
>>> +	mutex_unlock(&mhi_cntrl->pm_mutex);
>>> +	dev_dbg(dev, "Waiting for all pending threads to complete\n");
>>> +	wake_up_all(&mhi_cntrl->state_event);
>>> +
>>> +	dev_dbg(dev, "Reset all active channels and remove MHI
>devices\n");
>>> +	device_for_each_child(mhi_cntrl->cntrl_dev, NULL, 
>>> mhi_destroy_device);
>>> +
>>> +	mutex_lock(&mhi_cntrl->pm_mutex);
>>> +
>>> +	WARN_ON(atomic_read(&mhi_cntrl->dev_wake));
>>> +	WARN_ON(atomic_read(&mhi_cntrl->pending_pkts));
>>> +
>>> +	/* Reset the ev rings and cmd rings */
>>> +	dev_dbg(dev, "Resetting EV CTXT and CMD CTXT\n");
>>> +	mhi_cmd = mhi_cntrl->mhi_cmd;
>>> +	cmd_ctxt = mhi_cntrl->mhi_ctxt->cmd_ctxt;
>>> +	for (i = 0; i < NR_OF_CMD_RINGS; i++, mhi_cmd++, cmd_ctxt++) {
>>> +		struct mhi_ring *ring = &mhi_cmd->ring;
>>> +
>>> +		ring->rp = ring->base;
>>> +		ring->wp = ring->base;
>>> +		cmd_ctxt->rp = cmd_ctxt->rbase;
>>> +		cmd_ctxt->wp = cmd_ctxt->rbase;
>>> +	}
>>> +
>>> +	mhi_event = mhi_cntrl->mhi_event;
>>> +	er_ctxt = mhi_cntrl->mhi_ctxt->er_ctxt;
>>> +	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, er_ctxt++,
>>> +	     mhi_event++) {
>>> +		struct mhi_ring *ring = &mhi_event->ring;
>>> +
>>> +		/* Skip offload events */
>>> +		if (mhi_event->offload_ev)
>>> +			continue;
>>> +
>>> +		ring->rp = ring->base;
>>> +		ring->wp = ring->base;
>>> +		er_ctxt->rp = er_ctxt->rbase;
>>> +		er_ctxt->wp = er_ctxt->rbase;
>>> +	}
>>> +
>>> +	mhi_ready_state_transition(mhi_cntrl);
>>> +
>>> +exit_sys_error_transition:
>>>  	dev_dbg(dev, "Exiting with PM state: %s, MHI state: %s\n",
>>>  		to_mhi_pm_state_str(mhi_cntrl->pm_state),
>>>  		TO_MHI_STATE_STR(mhi_cntrl->dev_state));
>>> @@ -666,8 +782,7 @@ void mhi_pm_st_worker(struct work_struct *work)
>>>  			mhi_ready_state_transition(mhi_cntrl);
>>>  			break;
>>>  		case DEV_ST_TRANSITION_SYS_ERR:
>>> -			mhi_pm_disable_transition
>>> -				(mhi_cntrl, MHI_PM_SYS_ERR_PROCESS);
>>> +			mhi_pm_sys_error_transition(mhi_cntrl);
>>>  			break;
>>>  		case DEV_ST_TRANSITION_DISABLE:
>>>  			mhi_pm_disable_transition
>>> --
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>>> Forum,
>>> a Linux Foundation Collaborative Project
>>> 
>
>Thanks,
>Bhaumik

-- 
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