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Date:   Fri, 11 Jun 2021 11:06:32 +0800
From:   Can Guo <cang@codeaurora.org>
To:     Adrian Hunter <adrian.hunter@intel.com>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, ziqichen@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Kiwoong Kim <kwmad.kim@samsung.com>,
        Satya Tangirala <satyat@google.com>,
        Bart Van Assche <bvanassche@acm.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 7/9] scsi: ufs: Let host_sem cover the entire system
 suspend/resume
In-Reply-To: <6d31becb-98f8-2302-8ffa-657e6cadd8ec@intel.com>
References: <1623300218-9454-1-git-send-email-cang@codeaurora.org>
 <1623300218-9454-8-git-send-email-cang@codeaurora.org>
 <6d31becb-98f8-2302-8ffa-657e6cadd8ec@intel.com>
Message-ID: <eb268cc191916686f45c161f3f191049@codeaurora.org>
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Hi Adrian,

On 2021-06-10 21:32, Adrian Hunter wrote:
> On 10/06/21 7:43 am, Can Guo wrote:
>> UFS error handling now is doing more than just re-probing, but also 
>> sending
>> scsi cmds, e.g., for clearing UACs, and recovering runtime PM error, 
>> which
>> may change runtime status of scsi devices. To protect system 
>> suspend/resume
>> from being disturbed by error handling, move the host_sem from wl pm 
>> ops
>> to ufshcd_suspend_prepare() and ufshcd_resume_complete().
> 
> Have you checked whether error handling might actually be needed after
> ufshcd_suspend_prepare()?

I intend to make it this (simple) way - if error handling is invoked
during system suspend/resume, it should just wait until system resume
is finished. suspend/resume does not count on error handling, if 
suspend/resume
run into errors, they just fail and bail.

> 
> Wouldn't this complexity go away if we just did recovery
> directly in __ufshcd_wl_suspend() and  __ufshcd_wl_resume()?
> 

Please kindly check my reply in patch #5.

Thanks,
Can Guo.

>> 
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 8 +++-----
>>  drivers/scsi/ufs/ufshcd.h | 2 +-
>>  2 files changed, 4 insertions(+), 6 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index c418a19..861942b 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -9060,16 +9060,13 @@ static int ufshcd_wl_suspend(struct device 
>> *dev)
>>  	ktime_t start = ktime_get();
>> 
>>  	hba = shost_priv(sdev->host);
>> -	down(&hba->host_sem);
>> 
>>  	if (pm_runtime_suspended(dev))
>>  		goto out;
>> 
>>  	ret = __ufshcd_wl_suspend(hba, UFS_SYSTEM_PM);
>> -	if (ret) {
>> +	if (ret)
>>  		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
>> -		up(&hba->host_sem);
>> -	}
>> 
>>  out:
>>  	if (!ret)
>> @@ -9102,7 +9099,6 @@ static int ufshcd_wl_resume(struct device *dev)
>>  		hba->curr_dev_pwr_mode, hba->uic_link_state);
>>  	if (!ret)
>>  		hba->is_wl_sys_suspended = false;
>> -	up(&hba->host_sem);
>>  	return ret;
>>  }
>>  #endif
>> @@ -9665,6 +9661,7 @@ void ufshcd_resume_complete(struct device *dev)
>>  		ufshcd_rpmb_rpm_put(hba);
>>  		hba->rpmb_complete_put = false;
>>  	}
>> +	up(&hba->host_sem);
>>  }
>>  EXPORT_SYMBOL_GPL(ufshcd_resume_complete);
>> 
>> @@ -9691,6 +9688,7 @@ int ufshcd_suspend_prepare(struct device *dev)
>>  		ufshcd_rpmb_rpm_get_sync(hba);
>>  		hba->rpmb_complete_put = true;
>>  	}
>> +	down(&hba->host_sem);
>>  	return 0;
>>  }
>>  EXPORT_SYMBOL_GPL(ufshcd_suspend_prepare);
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index eaebb4e..47da47c 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -693,7 +693,7 @@ struct ufs_hba_monitor {
>>   * @ee_ctrl_mask: Exception event control mask
>>   * @is_powered: flag to check if HBA is powered
>>   * @shutting_down: flag to check if shutdown has been invoked
>> - * @host_sem: semaphore used to serialize concurrent contexts
>> + * @host_sem: semaphore used to avoid concurrency of contexts
>>   * @eh_wq: Workqueue that eh_work works on
>>   * @eh_work: Worker to handle UFS errors that require s/w attention
>>   * @eeh_work: Worker to handle exception events
>>