On Fri, Apr 22, 2022 at 10:19:14PM -0700, Bart Van Assche wrote: > 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? > yes! Thanks, Mani > > 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@xxxxxxx>
