linux-kernel - [PATCH 1/6] mmc: sdhci-s3c: Fix local I/O clock gating

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Date:	Tue, 24 Jun 2014 15:57:10 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	linux-samsung-soc@...r.kernel.org
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Kukjin Kim <kgene.kim@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Tomasz Figa <t.figa@...sung.com>,
	Ben Dooks <ben-linux@...ff.org>, Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org
Subject: [PATCH 1/6] mmc: sdhci-s3c: Fix local I/O clock gating

For internal card detection mechanism it is required that the local I/O
clock is always running. However while current implementation accounts
for this, it does so incorrectly leading to race conditions and warnings
about unbalanced clock disables.

This patch fixes it by inverting the logic, which now increases local
I/O clock enable count when internal card detect is used, instead of
decreasing it otherwise.

Signed-off-by: Tomasz Figa <t.figa@...sung.com>
Cc: Ben Dooks <ben-linux@...ff.org>
Cc: Chris Ball <chris@...ntf.net>
Cc: Ulf Hansson <ulf.hansson@...aro.org>
Cc: linux-mmc@...r.kernel.org
---
 drivers/mmc/host/sdhci-s3c.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index fa5954a..1795e1f 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -487,8 +487,13 @@ static int sdhci_s3c_probe(struct platform_device *pdev)
 		goto err_pdata_io_clk;
 	}
 
-	/* enable the local io clock and keep it running for the moment. */
-	clk_prepare_enable(sc->clk_io);
+	/*
+	 * Keep local I/O clock enabled for internal card detect pin
+	 * or runtime PM is disabled.
+	 */
+	if (pdata->cd_type == S3C_SDHCI_CD_INTERNAL
+	    || !IS_ENABLED(CONFIG_PM_RUNTIME))
+		clk_prepare_enable(sc->clk_io);
 
 	for (clks = 0, ptr = 0; ptr < MAX_BUS_CLK; ptr++) {
 		char name[14];
@@ -611,15 +616,13 @@ static int sdhci_s3c_probe(struct platform_device *pdev)
 		goto err_req_regs;
 	}
 
-#ifdef CONFIG_PM_RUNTIME
-	if (pdata->cd_type != S3C_SDHCI_CD_INTERNAL)
-		clk_disable_unprepare(sc->clk_io);
-#endif
 	return 0;
 
  err_req_regs:
  err_no_busclks:
-	clk_disable_unprepare(sc->clk_io);
+	if (pdata->cd_type == S3C_SDHCI_CD_INTERNAL
+	    || !IS_ENABLED(CONFIG_PM_RUNTIME))
+		clk_disable_unprepare(sc->clk_io);
 
  err_pdata_io_clk:
 	sdhci_free_host(host);
-- 
1.9.3

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