From 8d077ede48c1532d791c027467d152ae137c54ab Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 3 Dec 2021 15:19:49 -0800 Subject: [PATCH] scsi: ufs: Optimize the command queueing code Remove the clock scaling lock from ufshcd_queuecommand() since it is a performance bottleneck. Instead check the SCSI device budget bitmaps in the code that waits for ongoing ufshcd_queuecommand() calls. A bit is set in sdev->budget_map just before scsi_queue_rq() is called and a bit is cleared from that bitmap if scsi_queue_rq() does not submit the request or after the request has finished. See also the blk_mq_{get,put}_dispatch_budget() calls in the block layer. There is no risk for a livelock since the block layer delays queue reruns if queueing a request fails because the SCSI host has been blocked. Link: https://lore.kernel.org/r/20211203231950.193369-17-bvanassche@acm.org Cc: Asutosh Das (asd) Reviewed-by: Asutosh Das Signed-off-by: Bart Van Assche Signed-off-by: Martin K. Petersen --- drivers/scsi/ufs/ufshcd.c | 33 +++++++++++++++++++++++---------- drivers/scsi/ufs/ufshcd.h | 1 + 2 files changed, 24 insertions(+), 10 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 9f0a1f6..650dddf 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -1070,13 +1070,31 @@ static bool ufshcd_is_devfreq_scaling_required(struct ufs_hba *hba, return false; } +/* + * Determine the number of pending commands by counting the bits in the SCSI + * device budget maps. This approach has been selected because a bit is set in + * the budget map before scsi_host_queue_ready() checks the host_self_blocked + * flag. The host_self_blocked flag can be modified by calling + * scsi_block_requests() or scsi_unblock_requests(). + */ +static u32 ufshcd_pending_cmds(struct ufs_hba *hba) +{ + struct scsi_device *sdev; + u32 pending = 0; + + shost_for_each_device(sdev, hba->host) + pending += sbitmap_weight(&sdev->budget_map); + + return pending; +} + static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba, u64 wait_timeout_us) { unsigned long flags; int ret = 0; u32 tm_doorbell; - u32 tr_doorbell; + u32 tr_pending; bool timeout = false, do_last_check = false; ktime_t start; @@ -1094,8 +1112,8 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba, } tm_doorbell = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL); - tr_doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL); - if (!tm_doorbell && !tr_doorbell) { + tr_pending = ufshcd_pending_cmds(hba); + if (!tm_doorbell && !tr_pending) { timeout = false; break; } else if (do_last_check) { @@ -1115,12 +1133,12 @@ static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba, do_last_check = true; } spin_lock_irqsave(hba->host->host_lock, flags); - } while (tm_doorbell || tr_doorbell); + } while (tm_doorbell || tr_pending); if (timeout) { dev_err(hba->dev, "%s: timedout waiting for doorbell to clear (tm=0x%x, tr=0x%x)\n", - __func__, tm_doorbell, tr_doorbell); + __func__, tm_doorbell, tr_pending); ret = -EBUSY; } out: @@ -2681,9 +2699,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) WARN_ONCE(tag < 0, "Invalid tag %d\n", tag); - if (!down_read_trylock(&hba->clk_scaling_lock)) - return SCSI_MLQUEUE_HOST_BUSY; - /* * Allows the UFS error handler to wait for prior ufshcd_queuecommand() * calls. @@ -2772,8 +2787,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) out: rcu_read_unlock(); - up_read(&hba->clk_scaling_lock); - if (ufs_trigger_eh()) { unsigned long flags; diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h index 8e94276..88c20f3 100644 --- a/drivers/scsi/ufs/ufshcd.h +++ b/drivers/scsi/ufs/ufshcd.h @@ -778,6 +778,7 @@ struct ufs_hba_monitor { * @clk_list_head: UFS host controller clocks list node head * @pwr_info: holds current power mode * @max_pwr_info: keeps the device max valid pwm + * @clk_scaling_lock: used to serialize device commands and clock scaling * @desc_size: descriptor sizes reported by device * @urgent_bkops_lvl: keeps track of urgent bkops level for device * @is_urgent_bkops_lvl_checked: keeps track if the urgent bkops level for -- 2.7.4