Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()

[Baochen Qiang <quic_bqiang@xxxxxxxxxxx>]

On 2/29/2024 6:12 PM, Manivannan Sadhasivam wrote:
> On Wed, Feb 28, 2024 at 10:22:41AM +0800, Baochen Qiang wrote:
> > ath11k fails to resume:
> >
> > ath11k_pci 0000:06:00.0: timeout while waiting for restart complete
> >
> > This happens because when calling mhi_sync_power_up() the MHI subsystem
> > eventually calls device_add() from mhi_create_devices() but the device
> > creation is deferred:
> >
> > mhi mhi0_IPCR: Driver qcom_mhi_qrtr force probe deferral
> >
> > The reason for deferring device creation is explained in dpm_prepare():
> >
> >          /*
> >           * It is unsafe if probing of devices will happen during suspend or
> >           * hibernation and system behavior will be unpredictable in this case.
> >           * So, let's prohibit device's probing here and defer their probes
> >           * instead. The normal behavior will be restored in dpm_complete().
> >           */
> >
> > Because the device probe is deferred, the qcom_mhi_qrtr_probe() is not
> > called and thus MHI channels are not prepared:
> >
> > So what this means that QRTR is not delivering messages and the QMI connection
> > is not working between ath11k and the firmware, resulting a failure in firmware
> > initialization.
> >
> > To fix this add new function mhi_power_down_keep_dev() which doesn't destroy
> > the devices for channels during power down. This way we avoid probe defer issue
> > and finally can get ath11k hibernation working with the following patches.
> >
> > Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30
> >
> > Signed-off-by: Kalle Valo <quic_kvalo@xxxxxxxxxxx>
>
> Did Kalle co-author this patch? If so, his Co-developed-by tag should be
> added.
Hmm, I'm not sure...  I would like Kalle's thoughts on this.

> > Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
>
> - Mani
>
> > ---
> >   drivers/bus/mhi/host/internal.h |  4 +++-
> >   drivers/bus/mhi/host/pm.c       | 42 ++++++++++++++++++++++++++++-----
> >   include/linux/mhi.h             | 18 +++++++++++++-
> >   3 files changed, 56 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
> > index 5fe49311b8eb..aaad40a07f69 100644
> > --- a/drivers/bus/mhi/host/internal.h
> > +++ b/drivers/bus/mhi/host/internal.h
> > @@ -80,6 +80,7 @@ enum dev_st_transition {
> >   	DEV_ST_TRANSITION_FP,
> >   	DEV_ST_TRANSITION_SYS_ERR,
> >   	DEV_ST_TRANSITION_DISABLE,
> > +	DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE,
> >   	DEV_ST_TRANSITION_MAX,
> >   };
> >   
> > @@ -90,7 +91,8 @@ enum dev_st_transition {
> >   	dev_st_trans(MISSION_MODE,	"MISSION MODE")		\
> >   	dev_st_trans(FP,		"FLASH PROGRAMMER")	\
> >   	dev_st_trans(SYS_ERR,		"SYS ERROR")		\
> > -	dev_st_trans_end(DISABLE,	"DISABLE")
> > +	dev_st_trans(DISABLE,		"DISABLE")		\
> > +	dev_st_trans_end(DISABLE_DESTROY_DEVICE, "DISABLE (DESTROY DEVICE)")
> >   
> >   extern const char * const dev_state_tran_str[DEV_ST_TRANSITION_MAX];
> >   #define TO_DEV_STATE_TRANS_STR(state) (((state) >= DEV_ST_TRANSITION_MAX) ? \
> > diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> > index 8b40d3f01acc..11c0e751f223 100644
> > --- a/drivers/bus/mhi/host/pm.c
> > +++ b/drivers/bus/mhi/host/pm.c
> > @@ -468,7 +468,8 @@ static int mhi_pm_mission_mode_transition(struct mhi_controller *mhi_cntrl)
> >   }
> >   
> >   /* Handle shutdown transitions */
> > -static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
> > +static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl,
> > +				      bool destroy_device)
> >   {
> >   	enum mhi_pm_state cur_state;
> >   	struct mhi_event *mhi_event;
> > @@ -530,8 +531,16 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
> >   	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->mhi_dev->dev, NULL, mhi_destroy_device);
> > +	/*
> > +	 * Only destroy the 'struct device' for channels if indicated by the
> > +	 * 'destroy_device' flag. Because, during system suspend or hibernation
> > +	 * state, there is no need to destroy the 'struct device' as the endpoint
> > +	 * device would still be physically attached to the machine.
> > +	 */
> > +	if (destroy_device) {
> > +		dev_dbg(dev, "Reset all active channels and remove MHI devices\n");
> > +		device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_destroy_device);
> > +	}
> >   
> >   	mutex_lock(&mhi_cntrl->pm_mutex);
> >   
> > @@ -821,7 +830,10 @@ void mhi_pm_st_worker(struct work_struct *work)
> >   			mhi_pm_sys_error_transition(mhi_cntrl);
> >   			break;
> >   		case DEV_ST_TRANSITION_DISABLE:
> > -			mhi_pm_disable_transition(mhi_cntrl);
> > +			mhi_pm_disable_transition(mhi_cntrl, false);
> > +			break;
> > +		case DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE:
> > +			mhi_pm_disable_transition(mhi_cntrl, true);
> >   			break;
> >   		default:
> >   			break;
> > @@ -1175,7 +1187,8 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
> >   }
> >   EXPORT_SYMBOL_GPL(mhi_async_power_up);
> >   
> > -void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
> > +static void __mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful,
> > +			     bool destroy_device)
> >   {
> >   	enum mhi_pm_state cur_state, transition_state;
> >   	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > @@ -1211,15 +1224,32 @@ void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
> >   	write_unlock_irq(&mhi_cntrl->pm_lock);
> >   	mutex_unlock(&mhi_cntrl->pm_mutex);
> >   
> > -	mhi_queue_state_transition(mhi_cntrl, DEV_ST_TRANSITION_DISABLE);
> > +	if (destroy_device)
> > +		mhi_queue_state_transition(mhi_cntrl,
> > +					   DEV_ST_TRANSITION_DISABLE_DESTROY_DEVICE);
> > +	else
> > +		mhi_queue_state_transition(mhi_cntrl,
> > +					   DEV_ST_TRANSITION_DISABLE);
> >   
> >   	/* Wait for shutdown to complete */
> >   	flush_work(&mhi_cntrl->st_worker);
> >   
> >   	disable_irq(mhi_cntrl->irq[0]);
> >   }
> > +
> > +void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful)
> > +{
> > +	__mhi_power_down(mhi_cntrl, graceful, true);
> > +}
> >   EXPORT_SYMBOL_GPL(mhi_power_down);
> >   
> > +void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl,
> > +			       bool graceful)
> > +{
> > +	__mhi_power_down(mhi_cntrl, graceful, false);
> > +}
> > +EXPORT_SYMBOL_GPL(mhi_power_down_keep_dev);
> > +
> >   int mhi_sync_power_up(struct mhi_controller *mhi_cntrl)
> >   {
> >   	int ret = mhi_async_power_up(mhi_cntrl);
> > diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> > index 77b8c0a26674..cde01e133a1b 100644
> > --- a/include/linux/mhi.h
> > +++ b/include/linux/mhi.h
> > @@ -630,12 +630,28 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl);
> >   int mhi_sync_power_up(struct mhi_controller *mhi_cntrl);
> >   
> >   /**
> > - * mhi_power_down - Start MHI power down sequence
> > + * mhi_power_down - Power down the MHI device and also destroy the
> > + *                  'struct device' for the channels associated with it.
> > + *                  See also mhi_power_down_keep_dev() which is a variant
> > + *                  of this API that keeps the 'struct device' for channels
> > + *                  (useful during suspend/hibernation).
> >    * @mhi_cntrl: MHI controller
> >    * @graceful: Link is still accessible, so do a graceful shutdown process
> >    */
> >   void mhi_power_down(struct mhi_controller *mhi_cntrl, bool graceful);
> >   
> > +/**
> > + * mhi_power_down_keep_dev - Power down the MHI device but keep the 'struct
> > + *                           device' for the channels associated with it.
> > + *                           This is a variant of 'mhi_power_down()' and
> > + *                           useful in scenarios such as suspend/hibernation
> > + *                           where destroying of the 'struct device' is not
> > + *                           needed.
> > + * @mhi_cntrl: MHI controller
> > + * @graceful: Link is still accessible, so do a graceful shutdown process
> > + */
> > +void mhi_power_down_keep_dev(struct mhi_controller *mhi_cntrl, bool graceful);
> > +
> >   /**
> >    * mhi_unprepare_after_power_down - Free any allocated memory after power down
> >    * @mhi_cntrl: MHI controller
> > --
> > 2.25.1