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Subject: Re: [PATCH v3 7/9] scsi: ufs: Let host_sem cover the entire system
 suspend/resume
To:     Can Guo <cang@codeaurora.org>, asutoshd@codeaurora.org,
        nguyenb@codeaurora.org, hongwus@codeaurora.org,
        ziqichen@codeaurora.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com
Cc:     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>
References: <1623300218-9454-1-git-send-email-cang@codeaurora.org>
 <1623300218-9454-8-git-send-email-cang@codeaurora.org>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
Message-ID: <6d31becb-98f8-2302-8ffa-657e6cadd8ec@intel.com>
Date:   Thu, 10 Jun 2021 16:32:29 +0300
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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()?

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

> 
> 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
>