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Message-ID: <531daaa9-cf14-4812-8908-c617bd25bc08@quicinc.com>
Date: Thu, 29 Feb 2024 18:33:43 +0800
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Subject: Re: [PATCH v4 1/3] bus: mhi: host: add mhi_power_down_keep_dev()
Content-Language: en-US
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        "Kalle Valo
 (QUIC)" <quic_kvalo@quicinc.com>
CC: <ath11k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <mhi@lists.linux.dev>,
        <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
        <pabeni@redhat.com>, <netdev@vger.kernel.org>
References: <20240228022243.17762-1-quic_bqiang@quicinc.com>
 <20240228022243.17762-2-quic_bqiang@quicinc.com>
 <20240229101202.GB2999@thinkpad>
From: Baochen Qiang <quic_bqiang@quicinc.com>
In-Reply-To: <20240229101202.GB2999@thinkpad>
Content-Type: text/plain; charset="UTF-8"; format=flowed
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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@quicinc.com>
> 
> 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@quicinc.com>
> 
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> 
> - 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
>>
>