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Date:   Fri, 30 Oct 2020 12:34:07 -0700
From:   Bhaumik Bhatt <bbhatt@codeaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     linux-arm-msm@vger.kernel.org, hemantk@codeaurora.org,
        jhugo@codeaurora.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 10/12] bus: mhi: core: Separate system error and power
 down handling
Organization: Qualcomm Innovation Center, Inc.
Reply-To: bbhatt@codeaurora.org
Mail-Reply-To: bbhatt@codeaurora.org
In-Reply-To: <20201030140656.GL3818@Mani-XPS-13-9360>
References: <1604031057-32820-1-git-send-email-bbhatt@codeaurora.org>
 <1604031057-32820-11-git-send-email-bbhatt@codeaurora.org>
 <20201030140656.GL3818@Mani-XPS-13-9360>
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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.

>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.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
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum,
a Linux Foundation Collaborative Project