Messages in this thread | | | Date | Fri, 22 Apr 2022 22:19:14 -0700 | Subject | Re: [PATCH 4/5] scsi: ufs: core: Remove redundant wmb() in ufshcd_send_command() | From | Bart Van Assche <> |
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On 4/22/22 06:21, Manivannan Sadhasivam wrote: > The wmb() inside ufshcd_send_command() is added to make sure that the > doorbell is committed immediately.
That's not the purpose of the wmb() call so I think the comment is wrong.
> This leads to couple of expectations: > > 1. The doorbell write should complete before the function return. > 2. The doorbell write should not cross the function boundary. > > 2nd expectation is fullfilled by the Linux memory model as there is a > guarantee that the critical section won't cross the unlock (release) > operation.
I think you meant that the writel() won't cross the unlock operation?
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index 9349557b8a01..ec514a6c5393 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -2116,9 +2116,6 @@ void ufshcd_send_command(struct ufs_hba *hba, unsigned int task_tag) > __set_bit(task_tag, &hba->outstanding_reqs); > ufshcd_writel(hba, 1 << task_tag, REG_UTP_TRANSFER_REQ_DOOR_BELL); > spin_unlock_irqrestore(&hba->outstanding_lock, flags); > - > - /* Make sure that doorbell is committed immediately */ > - wmb(); > }
Anyway:
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
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