linux-kernel - [PATCH 4.19 010/346] scsi: ufs: Make sure clk scaling happens only when HBA is runtime ACTIVE

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Message-Id: <20201228124920.260848214@linuxfoundation.org>
Date:   Mon, 28 Dec 2020 13:45:29 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stanley Chu <stanley.chu@...iatek.com>,
        Can Guo <cang@...eaurora.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 010/346] scsi: ufs: Make sure clk scaling happens only when HBA is runtime ACTIVE

From: Can Guo <cang@...eaurora.org>

[ Upstream commit 73cc291c270248567245f084dcdf5078069af6b5 ]

If someone plays with the UFS clk scaling devfreq governor through sysfs,
ufshcd_devfreq_scale may be called even when HBA is not runtime ACTIVE.
This can lead to unexpected error. We cannot just protect it by calling
pm_runtime_get_sync() because that may cause a race condition since HBA
runtime suspend ops need to suspend clk scaling. To fix this call
pm_runtime_get_noresume() and check HBA's runtime status. Only proceed if
HBA is runtime ACTIVE, otherwise just bail.

governor_store
 devfreq_performance_handler
  update_devfreq
   devfreq_set_target
    ufshcd_devfreq_target
     ufshcd_devfreq_scale

Link: https://lore.kernel.org/r/1600758548-28576-1-git-send-email-cang@codeaurora.org
Reviewed-by: Stanley Chu <stanley.chu@...iatek.com>
Signed-off-by: Can Guo <cang@...eaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/ufs/ufshcd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 7e4e6e982055e..61b1eae42ea85 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1281,8 +1281,15 @@ static int ufshcd_devfreq_target(struct device *dev,
 	}
 	spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
 
+	pm_runtime_get_noresume(hba->dev);
+	if (!pm_runtime_active(hba->dev)) {
+		pm_runtime_put_noidle(hba->dev);
+		ret = -EAGAIN;
+		goto out;
+	}
 	start = ktime_get();
 	ret = ufshcd_devfreq_scale(hba, scale_up);
+	pm_runtime_put(hba->dev);
 
 	trace_ufshcd_profile_clk_scaling(dev_name(hba->dev),
 		(scale_up ? "up" : "down"),
-- 
2.27.0