linux-kernel - Re: [PATCH v4 7/7] scsi: ufs: Fix error handing during hibern8 enter

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Message-ID: <258c6c088cafb4c0b89e8e9439cfa06e@codeaurora.org>
Date:   Fri, 15 Nov 2019 09:33:22 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Avri Altman <Avri.Altman@....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,
        Subhash Jadavani <subhashj@...eaurora.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 7/7] scsi: ufs: Fix error handing during hibern8 enter

On 2019-11-14 19:06, Avri Altman wrote:
>> 
>> 
>> From: Subhash Jadavani <subhashj@...eaurora.org>
>> 
>> During clock gating (ufshcd_gate_work()), we first put the link 
>> hibern8 by
>> calling ufshcd_uic_hibern8_enter() and if ufshcd_uic_hibern8_enter() 
>> returns
>> success (0) then we gate all the clocks.
>> Now let’s zoom in to what ufshcd_uic_hibern8_enter() does internally:
>> It calls __ufshcd_uic_hibern8_enter() which on detecting the 
>> LINERESET,
>> initiates the full recovery and puts the link back to highest HS gear 
>> and returns
>> success (0) to ufshcd_uic_hibern8_enter() which is the issue as link 
>> is still in
>> active state due to recovery!
>> Now ufshcd_uic_hibern8_enter() returns success to ufshcd_gate_work() 
>> and
>> hence it goes ahead with gating the UFS clock while link is still in 
>> active state
>> hence I believe controller would raise UIC error interrupts. But when 
>> we service
>> the interrupt, clocks might have already been disabled!
>> 
>> This change fixes for this by returning failure from
>> __ufshcd_uic_hibern8_enter() if recovery succeeds as link is still not 
>> in hibern8,
>> upon receiving the error ufshcd_hibern8_enter() would initiate retry 
>> to put the
>> link state back into hibern8.
>> 
>> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 19 ++++++++++++++-----
>>  1 file changed, 14 insertions(+), 5 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c 
>> index
>> 7a5a904..934c27a 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -3891,15 +3891,24 @@ static int __ufshcd_uic_hibern8_enter(struct
>> ufs_hba *hba)
>>                              ktime_to_us(ktime_sub(ktime_get(), 
>> start)), ret);
>> 
>>         if (ret) {
>> +               int err;
>> +
>>                 dev_err(hba->dev, "%s: hibern8 enter failed. ret = 
>> %d\n",
>>                         __func__, ret);
>> 
>>                 /*
>> -                * If link recovery fails then return error so that 
>> caller
>> -                * don't retry the hibern8 enter again.
>> +                * If link recovery fails then return error code 
>> (-ENOLINK)
>> +                * returned ufshcd_link_recovery().
>> +                * If link recovery succeeds then return -EAGAIN to 
>> attempt
>> +                * hibern8 enter retry again.
> You no longer returning -ENOLINK, and either way retrying, regardless
> of the error code.
> Better check that the commit log is still telling the correct story,
> taking into consideration all those recent fixes and all.
> 

Thanks for pointing this.

Best Regards,
Can Guo.

>>                  */
>> -               if (ufshcd_link_recovery(hba))
>> -                       ret = -ENOLINK;
>> +               err = ufshcd_link_recovery(hba);
>> +               if (err) {
>> +                       dev_err(hba->dev, "%s: link recovery failed", 
>> __func__);
>> +                       ret = err;
>> +               } else {
>> +                       ret = -EAGAIN;
>> +               }
>>         } else
>>                 ufshcd_vops_hibern8_notify(hba, 
>> UIC_CMD_DME_HIBER_ENTER,
>>                                                                 
>> POST_CHANGE); @@ -3913,7 +3922,7 @@
>> static int ufshcd_uic_hibern8_enter(struct ufs_hba *hba)
>> 
>>         for (retries = UIC_HIBERN8_ENTER_RETRIES; retries > 0; 
>> retries--) {
>>                 ret = __ufshcd_uic_hibern8_enter(hba);
>> -               if (!ret || ret == -ENOLINK)
>> +               if (!ret)
>>                         goto out;
>>         }
>>  out:
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project