linux-kernel - [PATCH 3.16.y-ckt 030/183] mmc: sdhci-pxav3: fix unbalanced clock issues during probe

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Message-Id: <1425635874-19087-31-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  6 Mar 2015 09:55:21 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jisheng Zhang <jszhang@...vell.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 030/183] mmc: sdhci-pxav3: fix unbalanced clock issues during probe

3.16.7-ckt8 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jisheng Zhang <jszhang@...vell.com>

commit 62cf983ad84275f8580c807e5e596216c46773cf upstream.

Commit 0dcaa2499b7d ("sdhci-pxav3: Fix runtime PM initialization") tries
to fix one hang issue caused by calling sdhci_add_host() on a suspended
device. The fix enables the clock twice, once by clk_prepare_enable() and
another by pm_runtime_get_sync(), meaning that the clock will never be
gated at runtime PM suspend. I observed the power consumption regression on
Marvell BG2Q SoCs.

In fact, the fix is not correct. There still be a very small window
during which a runtime suspend might somehow occur after pm_runtime_enable()
but before pm_runtime_get_sync().

This patch fixes all of the two problems by just incrementing the usage
counter before pm_runtime_enable(). It also adjust the order of disabling
runtime pm and storing the usage count in the error path to handle clock
gating properly.

Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/mmc/host/sdhci-pxav3.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/host/sdhci-pxav3.c b/drivers/mmc/host/sdhci-pxav3.c
index bdfdf5273252..81143e57b2ff 100644
--- a/drivers/mmc/host/sdhci-pxav3.c
+++ b/drivers/mmc/host/sdhci-pxav3.c
@@ -356,10 +356,11 @@ static int sdhci_pxav3_probe(struct platform_device *pdev)
 		}
 	}

-	pm_runtime_enable(&pdev->dev);
-	pm_runtime_get_sync(&pdev->dev);
+	pm_runtime_get_noresume(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_set_autosuspend_delay(&pdev->dev, PXAV3_RPM_DELAY_MS);
 	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
 	pm_suspend_ignore_children(&pdev->dev, 1);

 	ret = sdhci_add_host(host);
@@ -382,8 +383,8 @@ static int sdhci_pxav3_probe(struct platform_device *pdev)
 	return 0;

 err_add_host:
-	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
 err_of_parse:
 err_cd_req:
 err_mbus_win:
--
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