linux-kernel - [PATCH 3.16 70/87] scsi: ufs: Avoid runtime suspend possibly being blocked forever

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Date:   Wed, 02 Oct 2019 20:06:51 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Avri Altman" <avri.altman@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Stanley Chu" <stanley.chu@...iatek.com>
Subject: [PATCH 3.16 70/87] scsi: ufs: Avoid runtime suspend possibly
 being blocked forever

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stanley Chu <stanley.chu@...iatek.com>

commit 24e2e7a19f7e4b83d0d5189040d997bce3596473 upstream.

UFS runtime suspend can be triggered after pm_runtime_enable() is invoked
in ufshcd_pltfrm_init(). However if the first runtime suspend is triggered
before binding ufs_hba structure to ufs device structure via
platform_set_drvdata(), then UFS runtime suspend will be no longer
triggered in the future because its dev->power.runtime_error was set in the
first triggering and does not have any chance to be cleared.

To be more clear, dev->power.runtime_error is set if hba is NULL in
ufshcd_runtime_suspend() which returns -EINVAL to rpm_callback() where
dev->power.runtime_error is set as -EINVAL. In this case, any future
rpm_suspend() for UFS device fails because rpm_check_suspend_allowed()
fails due to non-zero
dev->power.runtime_error.

To resolve this issue, make sure the first UFS runtime suspend get valid
"hba" in ufshcd_runtime_suspend(): Enable UFS runtime PM only after hba is
successfully bound to UFS device structure.

Fixes: 62694735ca95 ([SCSI] ufs: Add runtime PM support for UFS host controller driver)
Signed-off-by: Stanley Chu <stanley.chu@...iatek.com>
Reviewed-by: Avri Altman <avri.altman@....com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
[bwh: Backported to 3.16:
 - ufshcd_pltrfm_probe() doesn't allocate or free the host structure
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/ufs/ufshcd-pltfrm.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/drivers/scsi/ufs/ufshcd-pltfrm.c
+++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
@@ -150,22 +150,19 @@ static int ufshcd_pltfrm_probe(struct pl
 		goto out;
 	}

-	pm_runtime_set_active(&pdev->dev);
-	pm_runtime_enable(&pdev->dev);
-
 	err = ufshcd_init(dev, &hba, mmio_base, irq);
 	if (err) {
 		dev_err(dev, "Intialization failed\n");
-		goto out_disable_rpm;
+		goto out;
 	}

 	platform_set_drvdata(pdev, hba);

+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
 	return 0;

-out_disable_rpm:
-	pm_runtime_disable(&pdev->dev);
-	pm_runtime_set_suspended(&pdev->dev);
 out:
 	return err;
 }