scsi: ufs: core: Fix abnormal scale up after scale down

When no active_reqs, devfreq_monitor (thread A) will suspend clock scaling.
But it may have racing with clk_scaling.suspend_work (thread B) and
actually not suspend clock scaling (requeue after suspend).  Next time
after polling_ms, devfreq_monitor read clk_scaling.window_start_t = 0 then
scale up clock abnormal.

Below is racing step:
	devfreq->work (Thread A)
	devfreq_monitor
		update_devfreq
		.....
			ufshcd_devfreq_target
			queue_work(hba->clk_scaling.workq,
1			   &hba->clk_scaling.suspend_work)
		.....
5	queue_delayed_work(devfreq_wq, &devfreq->work,
			msecs_to_jiffies(devfreq->profile->polling_ms));

2	hba->clk_scaling.suspend_work (Thread B)
	ufshcd_clk_scaling_suspend_work
		__ufshcd_suspend_clkscaling
			devfreq_suspend_device(hba->devfreq);
3				cancel_delayed_work_sync(&devfreq->work);
4			hba->clk_scaling.window_start_t = 0;
	.....

Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Link: https://lore.kernel.org/r/20230831130826.5592-4-peter.wang@mediatek.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 729f49cfff4c25b09aac8141ee8f3ba8cd12fa0c..af576d3606f609a594672aafe7cd616868120929 100644 (file)
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1402,6 +1402,13 @@ static int ufshcd_devfreq_target(struct device *dev,
                return 0;
        }
 
+       /* Skip scaling clock when clock scaling is suspended */
+       if (hba->clk_scaling.is_suspended) {
+               spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
+               dev_warn(hba->dev, "clock scaling is suspended, skip");
+               return 0;
+       }
+
        if (!hba->clk_scaling.active_reqs)
                sched_clk_scaling_suspend_work = true;