All of lore.kernel.org
 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 \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.