Date:   Mon, 02 Nov 2020 08:52:44 -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
Subject: Re: [PATCH v3 10/12] bus: mhi: core: Separate system error and power
 down handling

Hi Mani,

On 2020-10-30 23:54, Manivannan Sadhasivam wrote:
> 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
> 
It had to be done for 11/12 and 12/12 (last two) patches of the series. 
It's a
much cleaner approach and allows us to handle states better. We should 
be moving
the dev_state and EE to "Reset" and "Disable" states soon enough when a 
shutdown
is initiated and we can resolve bugs such as freeing the IRQs for a 
shutdown
sooner as well. Since these differences in shutdown versus SYS_ERROR 
processing
are already increasingly apparent and more could come, this patch had to 
step
in.

bus: mhi: core: Mark and maintain device states early on after power 
down
bus: mhi: core: Remove MHI event ring IRQ handlers when powering down
>>>> 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

Thanks,
Bhaumik
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum,
a Linux Foundation Collaborative Project

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