linux-scsi.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bart Van Assche <bvanassche@acm.org>
To: Can Guo <cang@codeaurora.org>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	linux-scsi@vger.kernel.org, Bean Huo <beanhuo@micron.com>,
	Avri Altman <avri.altman@wdc.com>,
	Stanley Chu <stanley.chu@mediatek.com>,
	Tomas Winkler <tomas.winkler@intel.com>
Subject: Re: [PATCH 5/6] ufs: Remove superfluous memory barriers
Date: Thu, 26 Dec 2019 09:36:19 -0800	[thread overview]
Message-ID: <8eacc776-5a06-b984-8c26-39d0cbaa9d9a@acm.org> (raw)
In-Reply-To: <aba850f956421c187e0b88343f6d5070@codeaurora.org>

On 12/25/19 2:31 AM, Can Guo wrote:
> On 2019-12-25 06:02, Bart Van Assche wrote:
>> Calling wmb() after having written to a doorbell slows down code and does
>> not help to commit the doorbell write faster. Hence remove such wmb()
>> calls. Note: detailed information about the semantics of writel() is
>> available in Documentation/driver-api/device-io.rst.
>>
>> Cc: Bean Huo <beanhuo@micron.com>
>> Cc: Can Guo <cang@codeaurora.org>
>> Cc: Avri Altman <avri.altman@wdc.com>
>> Cc: Stanley Chu <stanley.chu@mediatek.com>
>> Cc: Tomas Winkler <tomas.winkler@intel.com>
>> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 4 ----
>>  1 file changed, 4 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 4d9bb1932b39..edcc137c436b 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -1879,8 +1879,6 @@ void ufshcd_send_command(struct ufs_hba *hba,
>> unsigned int task_tag)
>>      ufshcd_clk_scaling_start_busy(hba);
>>      __set_bit(task_tag, &hba->outstanding_reqs);
>>      ufshcd_writel(hba, 1 << task_tag, REG_UTP_TRANSFER_REQ_DOOR_BELL);
>> -    /* Make sure that doorbell is committed immediately */
>> -    wmb();
>>  }
>>
>>  /**
>> @@ -5766,8 +5764,6 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba 
>> *hba,
>>      wmb();
>>
>>      ufshcd_writel(hba, 1 << free_slot, REG_UTP_TASK_REQ_DOOR_BELL);
>> -    /* Make sure that doorbell is committed immediately */
>> -    wmb();
>>
>>      spin_unlock_irqrestore(host->host_lock, flags);
> 
> Hi Bart,
> 
> Three wmb()s were added in commit ad1a1b9cd because we did see instances on
> which OCS=3(MISMATCH_DATA_BUFFER_SIZE) error were observed in large scale
> test. Commit ad1a1b9cd fixed the error and we had confirmed it through
> large amount of tests. I am not sure removing the 2 wmb()s here would cause
> regression or not.

Hi Can,

Thank you for having reported this. I will drop this patch.

Bart.

  reply	other threads:[~2019-12-26 17:36 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-24 22:02 [PATCH 0/6] Six UFS patches Bart Van Assche
2019-12-24 22:02 ` [PATCH 1/6] ufs: Fix indentation in ufshcd_query_attr_retry() Bart Van Assche
2019-12-25  7:16   ` Stanley Chu
2019-12-25  8:17   ` Can Guo
2019-12-27  1:13   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 2/6] ufs: Make ufshcd_add_command_trace() easier to read Bart Van Assche
2019-12-25  7:16   ` Stanley Chu
2019-12-25  8:17   ` Can Guo
2019-12-27  1:17   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 3/6] ufs: Make ufshcd_prepare_utp_scsi_cmd_upiu() " Bart Van Assche
2019-12-25  7:17   ` Stanley Chu
2019-12-25  8:18   ` Can Guo
2019-12-24 22:02 ` [PATCH 4/6] ufs: Fix a race condition in the tracing code Bart Van Assche
2019-12-25 10:59   ` Can Guo
2019-12-26 17:35     ` Bart Van Assche
2019-12-27  5:50       ` Can Guo
2019-12-27  1:21   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 5/6] ufs: Remove superfluous memory barriers Bart Van Assche
2019-12-25 10:31   ` Can Guo
2019-12-26 17:36     ` Bart Van Assche [this message]
2019-12-24 22:02 ` [PATCH 6/6] ufs: Remove the SCSI timeout handler Bart Van Assche
2019-12-25 11:02   ` Can Guo
2019-12-27  1:24   ` Alim Akhtar
2020-05-28  9:47   ` Can Guo
2020-05-28 16:12     ` Bart Van Assche
2020-05-29  1:39       ` Can Guo
2020-05-29  3:56         ` Bart Van Assche
2020-01-03  2:58 ` [PATCH 0/6] Six UFS patches Martin K. Petersen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=8eacc776-5a06-b984-8c26-39d0cbaa9d9a@acm.org \
    --to=bvanassche@acm.org \
    --cc=avri.altman@wdc.com \
    --cc=beanhuo@micron.com \
    --cc=cang@codeaurora.org \
    --cc=jejb@linux.vnet.ibm.com \
    --cc=linux-scsi@vger.kernel.org \
    --cc=martin.petersen@oracle.com \
    --cc=stanley.chu@mediatek.com \
    --cc=tomas.winkler@intel.com \
    --subject='Re: [PATCH 5/6] ufs: Remove superfluous memory barriers' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox