From: Manivannan Sadhasivam Date: Wed, 4 May 2022 08:42:11 +0000 (+0530) Subject: scsi: ufs: core: Remove redundant wmb() in ufshcd_send_command() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=23803bacaab47eafcd3a13ab607b5aa7b0debaaf;p=linux.git scsi: ufs: core: Remove redundant wmb() in ufshcd_send_command() The wmb() inside ufshcd_send_command() is added to make sure that the doorbell is committed immediately. 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. 1st expectation is not really needed here as there is no following read/ write that depends on the doorbell to be complete implicitly. Even if the doorbell write is in a CPUs Write Buffer (WB), wmb() won't flush it. And there is no real need of a WB flush here as well. So let's get rid of the wmb() that seems redundant. Link: https://lore.kernel.org/r/20220504084212.11605-5-manivannan.sadhasivam@linaro.org Reviewed-by: Bart Van Assche Reviewed-by: Bjorn Andersson Acked-by: Bean Huo Signed-off-by: Manivannan Sadhasivam Signed-off-by: Martin K. Petersen --- diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 2b4390a1106e2..1f82590d153fc 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -2143,9 +2143,6 @@ 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(); } /**