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Date:   Thu, 16 Jul 2020 11:38:33 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To:     bbhatt@codeaurora.org
Cc:     linux-arm-msm@vger.kernel.org, hemantk@codeaurora.org,
        jhugo@codeaurora.org, linux-kernel@vger.kernel.org,
        linux-arm-msm-owner@vger.kernel.org
Subject: Re: [PATCH v4 3/9] bus: mhi: core: Use helper API to trigger a
 non-blocking host resume
Message-ID: <20200716060833.GE3271@Mani-XPS-13-9360>
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On Wed, Jul 08, 2020 at 01:53:49PM -0700, bbhatt@codeaurora.org wrote:
> On 2020-07-04 07:47, Manivannan Sadhasivam wrote:
> > On Mon, Jun 29, 2020 at 09:39:36AM -0700, Bhaumik Bhatt wrote:
> > > Autonomous low power mode support requires the MHI host to resume from
> > > multiple places and post a wakeup source to exit system suspend. This
> > > needs to be done in a non-blocking manner. Introduce a helper API to
> > > trigger the host resume for data transfers and other non-blocking use
> > > cases while supporting implementation of autonomous low power modes.
> > > 
> > 
> > Why can't you use pm_wakeup_event() as done in __mhi_device_get_sync()?
> > 
> > Thanks,
> > Mani
> > 
> 
> I forgot to address the __mhi_device_get_sync() function. Thanks for
> pointing out.
> 
> Is it preferable to always post wakeup source with hard boolean set?

A quick grep shows that this routine is not used extensively as compared to
the other one and hence the question.

For a bus driver like this I think we can just live without the hard wakeup.
I don't see a specific usecase where we would need a hard wakeup from suspend.

Thanks,
Mani

> We do want to wakeup from Suspend-to-Idle if system suspend happens to go
> that route.
> 
> As of now, we just by default do regular wakeup event and not hard.
> I figured at some point we might need to distinguish between hard vs
> regular, hence the option but
> it can be eliminated in favor of one or another.
> 


> Thanks,
> Bhaumik
> 
> > > Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> > > ---
> > >  drivers/bus/mhi/core/internal.h |  8 ++++++++
> > >  drivers/bus/mhi/core/main.c     | 21 +++++++--------------
> > >  drivers/bus/mhi/core/pm.c       |  6 ++----
> > >  3 files changed, 17 insertions(+), 18 deletions(-)
> > > 
> > > diff --git a/drivers/bus/mhi/core/internal.h
> > > b/drivers/bus/mhi/core/internal.h
> > > index bcfa7b6..cb32eaf 100644
> > > --- a/drivers/bus/mhi/core/internal.h
> > > +++ b/drivers/bus/mhi/core/internal.h
> > > @@ -599,6 +599,14 @@ int mhi_queue_state_transition(struct
> > > mhi_controller *mhi_cntrl,
> > >  int mhi_send_cmd(struct mhi_controller *mhi_cntrl, struct mhi_chan
> > > *mhi_chan,
> > >  		 enum mhi_cmd_type cmd);
> > > 
> > > +static inline void mhi_trigger_resume(struct mhi_controller
> > > *mhi_cntrl,
> > > +				      bool hard_wakeup)
> > > +{
> > > +	pm_wakeup_dev_event(&mhi_cntrl->mhi_dev->dev, 0, hard_wakeup);
> > > +	mhi_cntrl->runtime_get(mhi_cntrl);
> > > +	mhi_cntrl->runtime_put(mhi_cntrl);
> > > +}
> > > +
> > >  /* Register access methods */
> > >  void mhi_db_brstmode(struct mhi_controller *mhi_cntrl, struct
> > > db_cfg *db_cfg,
> > >  		     void __iomem *db_addr, dma_addr_t db_val);
> > > diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> > > index 1f622ce..8d6ec34 100644
> > > --- a/drivers/bus/mhi/core/main.c
> > > +++ b/drivers/bus/mhi/core/main.c
> > > @@ -909,8 +909,7 @@ void mhi_ctrl_ev_task(unsigned long data)
> > >  		 * process it since we are probably in a suspended state,
> > >  		 * so trigger a resume.
> > >  		 */
> > > -		mhi_cntrl->runtime_get(mhi_cntrl);
> > > -		mhi_cntrl->runtime_put(mhi_cntrl);
> > > +		mhi_trigger_resume(mhi_cntrl, false);
> > > 
> > >  		return;
> > >  	}
> > > @@ -971,10 +970,8 @@ int mhi_queue_skb(struct mhi_device *mhi_dev,
> > > enum dma_data_direction dir,
> > >  	}
> > > 
> > >  	/* we're in M3 or transitioning to M3 */
> > > -	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state)) {
> > > -		mhi_cntrl->runtime_get(mhi_cntrl);
> > > -		mhi_cntrl->runtime_put(mhi_cntrl);
> > > -	}
> > > +	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
> > > +		mhi_trigger_resume(mhi_cntrl, false);
> > > 
> > >  	/* Toggle wake to exit out of M2 */
> > >  	mhi_cntrl->wake_toggle(mhi_cntrl);
> > > @@ -1032,10 +1029,8 @@ int mhi_queue_dma(struct mhi_device *mhi_dev,
> > > enum dma_data_direction dir,
> > >  	}
> > > 
> > >  	/* we're in M3 or transitioning to M3 */
> > > -	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state)) {
> > > -		mhi_cntrl->runtime_get(mhi_cntrl);
> > > -		mhi_cntrl->runtime_put(mhi_cntrl);
> > > -	}
> > > +	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
> > > +		mhi_trigger_resume(mhi_cntrl, false);
> > > 
> > >  	/* Toggle wake to exit out of M2 */
> > >  	mhi_cntrl->wake_toggle(mhi_cntrl);
> > > @@ -1147,10 +1142,8 @@ int mhi_queue_buf(struct mhi_device *mhi_dev,
> > > enum dma_data_direction dir,
> > >  	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
> > > 
> > >  	/* we're in M3 or transitioning to M3 */
> > > -	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state)) {
> > > -		mhi_cntrl->runtime_get(mhi_cntrl);
> > > -		mhi_cntrl->runtime_put(mhi_cntrl);
> > > -	}
> > > +	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
> > > +		mhi_trigger_resume(mhi_cntrl, false);
> > > 
> > >  	/* Toggle wake to exit out of M2 */
> > >  	mhi_cntrl->wake_toggle(mhi_cntrl);
> > > diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
> > > index 661d704..5e3994e 100644
> > > --- a/drivers/bus/mhi/core/pm.c
> > > +++ b/drivers/bus/mhi/core/pm.c
> > > @@ -1139,10 +1139,8 @@ void mhi_device_put(struct mhi_device *mhi_dev)
> > > 
> > >  	mhi_dev->dev_wake--;
> > >  	read_lock_bh(&mhi_cntrl->pm_lock);
> > > -	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state)) {
> > > -		mhi_cntrl->runtime_get(mhi_cntrl);
> > > -		mhi_cntrl->runtime_put(mhi_cntrl);
> > > -	}
> > > +	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
> > > +		mhi_trigger_resume(mhi_cntrl, false);
> > > 
> > >  	mhi_cntrl->wake_put(mhi_cntrl, false);
> > >  	read_unlock_bh(&mhi_cntrl->pm_lock);
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum,
> > > a Linux Foundation Collaborative Project
> > >