linux-kernel - Re: [PATCH v5 3/7] scsi: ufs: Fix up auto hibern8 enablement

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Date:   Fri, 15 Nov 2019 15:03:37 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Stanley Chu <stanley.chu@...iatek.com>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Bean Huo <beanhuo@...ron.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3/7] scsi: ufs: Fix up auto hibern8 enablement

On 2019-11-15 14:35, Stanley Chu wrote:
> Hi Can,
> 
> On Thu, 2019-11-14 at 22:09 -0800, Can Guo wrote:
>> +	if (hba->ahit != ahit)
>> +		hba->ahit = ahit;
>>  	spin_unlock_irqrestore(hba->host->host_lock, flags);
>> +	if (!pm_runtime_suspended(hba->dev)) {
> 
> Always do pm_runtime_get_sync() here could avoid possible racing?
> 
> And thus AH8 could be enabled regardless of runtime status.
> 
>> +		pm_runtime_get_sync(hba->dev);
>> +		ufshcd_hold(hba, false);
>> +		ufshcd_auto_hibern8_enable(hba);
>> +		ufshcd_release(hba);
>> +		pm_runtime_put(hba->dev);
>> +	}
>>  }
> 
> Thanks,
> Stanley

Hi Stanley,

if !pm_runtime_suspended() is true, hba->dev's runtime status, other 
than RPM_ACTIVE,
may be RPM_SUSPENDING or RPM_RESUMING. So, here for safty, do 
pm_runtime_get_sync() once
before access registers, in case we hit corner cases in which powers 
and/or clocks are OFF.

Thanks,
Can Guo.