[PATCH] [NAND] S3C2410: Fix NFC clock enable/disable imbalance (2nd try)

[Juergen Beisert]

When unmounting an mtd filesystem the s3c2410_nand_select_chip() function
gets called again with "chip == -1". In this case the current code disables
the NFC clock at least a second time, so it does not work anymore.
Clock disabling should only happen if it was really enabled.

Due to a lack of a query function if a clock is already enabled (and how often),
we must count enable/disable calls by our own here.

Note: Other enable/disable sequences can be found in the power management
functions. I'm not sure if they interfere with this local enable/disable count.

Signed-off-by: Juergen Beisert <jbe at pengutronix.de>
Acked-by: Wolfram Sang <wsa at pengutronix.de>

---
 drivers/mtd/nand/s3c2410.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Index: linux-2.6.32/drivers/mtd/nand/s3c2410.c
===================================================================
--- linux-2.6.32.orig/drivers/mtd/nand/s3c2410.c
+++ linux-2.6.32/drivers/mtd/nand/s3c2410.c
@@ -329,12 +329,15 @@ static void s3c2410_nand_select_chip(str
 	struct s3c2410_nand_mtd *nmtd;
 	struct nand_chip *this = mtd->priv;
 	unsigned long cur;
+	static int clock_enable_cnt = 0;
 
 	nmtd = this->priv;
 	info = nmtd->info;
 
-	if (chip != -1 && allow_clk_stop(info))
+	if (chip != -1 && allow_clk_stop(info)) {
 		clk_enable(info->clk);
+		clock_enable_cnt++;
+	}
 
 	cur = readl(info->sel_reg);
 
@@ -356,8 +359,10 @@ static void s3c2410_nand_select_chip(str
 
 	writel(cur, info->sel_reg);
 
-	if (chip == -1 && allow_clk_stop(info))
+	if (chip == -1 && allow_clk_stop(info) && clock_enable_cnt > 0) {
 		clk_disable(info->clk);
+		clock_enable_cnt--;
+	}
 }
 
 /* s3c2410_nand_hwcontrol

-- 
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