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FROMLIST: ufs: core: fix abnormal scale up after scale down

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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(requue 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;
	.....

Bug: 298004596
Link: https://lore.kernel.org/all/20230831130826.5592-4-peter.wang@mediatek.com/
Change-Id: I3ea77255f1b3845e9dd7bf6b050f3e9ba1f5f3f2
Signed-off-by: Peter Wang <peter.wang@mediatek.com>
This commit is contained in:
Peter Wang 2023-08-23 17:29:48 +08:00 committed by Saravana Kannan
parent e490b62fed
commit 89434cbd2d
1 changed files with 7 additions and 0 deletions
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7
drivers/ufs/core/ufshcd.c
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@ -1464,6 +1464,13 @@ 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;