From 3d2ac73d13476fd996e3423863371805780a0663 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Wed, 21 Jul 2021 20:34:30 -0700 Subject: [PATCH] scsi: ufs: Remove several wmb() calls From arch/arm/include/asm/io.h #define __iowmb() wmb() [ ... ] #define writel(v,c) ({ __iowmb(); writel_relaxed(v,c); }) From Documentation/memory-barriers.txt: "Note that, when using writel(), a prior wmb() is not needed to guarantee that the cache coherent memory writes have completed before writing to the MMIO region." In other words, calling wmb() before writel() is not necessary. Hence remove the wmb() calls that precede a writel() call. Remove the wmb() calls that precede a ufshcd_send_command() call since the latter function uses writel(). Remove the wmb() call from ufshcd_wait_for_dev_cmd() since the following chain of events guarantees that the CPU will see up-to-date LRB values: - UFS controller writes to host memory. - UFS controller posts completion interrupt after the memory writes from the previous step are visible to the CPU. - complete(hba->dev_cmd.complete) is called from the UFS interrupt handler. - The wait_for_completion(hba->dev_cmd.complete) call in ufshcd_wait_for_dev_cmd() returns. Link: https://lore.kernel.org/r/20210722033439.26550-10-bvanassche@acm.org Cc: Adrian Hunter Cc: Stanley Chu Cc: Can Guo Cc: Asutosh Das Cc: Avri Altman Tested-by: Avri altman Reviewed-by: Avri Altman Reviewed-by: Daejun Park Signed-off-by: Bart Van Assche Signed-off-by: Martin K. Petersen --- drivers/scsi/ufs/ufshcd.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 3ef2a2dda700..867678ea23ad 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -2777,8 +2777,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) ufshcd_release(hba); goto out; } - /* Make sure descriptors are ready before ringing the doorbell */ - wmb(); ufshcd_send_command(hba, tag); out: @@ -2888,8 +2886,6 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba, time_left = wait_for_completion_timeout(hba->dev_cmd.complete, msecs_to_jiffies(max_timeout)); - /* Make sure descriptors are ready before ringing the doorbell */ - wmb(); spin_lock_irqsave(hba->host->host_lock, flags); hba->dev_cmd.complete = NULL; if (likely(time_left)) { @@ -2968,8 +2964,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba, hba->dev_cmd.complete = &wait; ufshcd_add_query_upiu_trace(hba, UFS_QUERY_SEND, lrbp->ucd_req_ptr); - /* Make sure descriptors are ready before ringing the doorbell */ - wmb(); ufshcd_send_command(hba, tag); err = ufshcd_wait_for_dev_cmd(hba, lrbp, timeout); @@ -6557,9 +6551,6 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba, /* send command to the controller */ __set_bit(task_tag, &hba->outstanding_tasks); - /* Make sure descriptors are ready before ringing the task doorbell */ - wmb(); - ufshcd_writel(hba, 1 << task_tag, REG_UTP_TASK_REQ_DOOR_BELL); /* Make sure that doorbell is committed immediately */ wmb(); @@ -6731,8 +6722,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba, hba->dev_cmd.complete = &wait; ufshcd_add_query_upiu_trace(hba, UFS_QUERY_SEND, lrbp->ucd_req_ptr); - /* Make sure descriptors are ready before ringing the doorbell */ - wmb(); ufshcd_send_command(hba, tag); /* -- 2.11.0