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Subject[PATCH 1/2] nand: Fix S3C NAND clock stop
Date
Current implementation of s3c2410_nand_select_chip call
clk_disable every time when chip = -1 (de-select). This happend
multiple times even if chip was already de-selected. This causes
disabling clock even if they are already disabled and due to
nature of clock subsytem implementation this causes nand clock
to be disabled and newer enabled again.

Signed-off-by: Jiri Pinkava <jiri.pinkava@vscht.cz>
---
drivers/mtd/nand/s3c2410.c | 59 ++++++++++++++++++++++++++++++++------------
1 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/drivers/mtd/nand/s3c2410.c b/drivers/mtd/nand/s3c2410.c
index 33d832d..cea775a 100644
--- a/drivers/mtd/nand/s3c2410.c
+++ b/drivers/mtd/nand/s3c2410.c
@@ -55,7 +55,7 @@ static int hardware_ecc = 0;
#endif

#ifdef CONFIG_MTD_NAND_S3C2410_CLKSTOP
-static int clock_stop = 1;
+static const int clock_stop = 1;
#else
static const int clock_stop = 0;
#endif
@@ -96,6 +96,12 @@ enum s3c_cpu_type {
TYPE_S3C2440,
};

+enum s3c_nand_clk_state {
+ CLOCK_DISABLE = 0,
+ CLOCK_ENABLE,
+ CLOCK_SUSPEND,
+};
+
/* overview of the s3c2410 nand state */

/**
@@ -111,6 +117,7 @@ enum s3c_cpu_type {
* @mtd_count: The number of MTDs created from this controller.
* @save_sel: The contents of @sel_reg to be saved over suspend.
* @clk_rate: The clock rate from @clk.
+ * @clk_state: The current clock state.
* @cpu_type: The exact type of this controller.
*/
struct s3c2410_nand_info {
@@ -129,6 +136,7 @@ struct s3c2410_nand_info {
int mtd_count;
unsigned long save_sel;
unsigned long clk_rate;
+ enum s3c_nand_clk_state clk_state;

enum s3c_cpu_type cpu_type;

@@ -159,11 +167,33 @@ static struct s3c2410_platform_nand *to_nand_plat(struct platform_device *dev)
return dev->dev.platform_data;
}

-static inline int allow_clk_stop(struct s3c2410_nand_info *info)
+static inline int allow_clk_suspend(struct s3c2410_nand_info *info)
{
return clock_stop;
}

+/**
+ * s3c2410_nand_clk_set_state - Enable, disable or suspend NAND clock.
+ * @info: The controller instance.
+ * @new_state: State to which clock should be set.
+ */
+static void s3c2410_nand_clk_set_state(struct s3c2410_nand_info *info,
+ enum s3c_nand_clk_state new_state)
+{
+ if (!allow_clk_suspend(info) && new_state == CLOCK_SUSPEND)
+ return;
+
+ if (info->clk_state == CLOCK_ENABLE) {
+ if (new_state != CLOCK_ENABLE)
+ clk_disable(info->clk);
+ } else {
+ if (new_state == CLOCK_ENABLE)
+ clk_enable(info->clk);
+ }
+
+ info->clk_state = new_state;
+}
+
/* timing calculations */

#define NS_IN_KHZ 1000000
@@ -333,8 +363,8 @@ static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)
nmtd = this->priv;
info = nmtd->info;

- if (chip != -1 && allow_clk_stop(info))
- clk_enable(info->clk);
+ if (chip != -1)
+ s3c2410_nand_clk_set_state(info, CLOCK_ENABLE);

cur = readl(info->sel_reg);

@@ -356,8 +386,8 @@ static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)

writel(cur, info->sel_reg);

- if (chip == -1 && allow_clk_stop(info))
- clk_disable(info->clk);
+ if (chip == -1)
+ s3c2410_nand_clk_set_state(info, CLOCK_SUSPEND);
}

/* s3c2410_nand_hwcontrol
@@ -694,8 +724,7 @@ static int s3c24xx_nand_remove(struct platform_device *pdev)
/* free the common resources */

if (info->clk != NULL && !IS_ERR(info->clk)) {
- if (!allow_clk_stop(info))
- clk_disable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_DISABLE);
clk_put(info->clk);
}

@@ -947,7 +976,7 @@ static int s3c24xx_nand_probe(struct platform_device *pdev)
goto exit_error;
}

- clk_enable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_ENABLE);

/* allocate and map the resource */

@@ -1026,9 +1055,9 @@ static int s3c24xx_nand_probe(struct platform_device *pdev)
goto exit_error;
}

- if (allow_clk_stop(info)) {
+ if (allow_clk_suspend(info)) {
dev_info(&pdev->dev, "clock idle support enabled\n");
- clk_disable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_SUSPEND);
}

pr_debug("initialised ok\n");
@@ -1059,8 +1088,7 @@ static int s3c24xx_nand_suspend(struct platform_device *dev, pm_message_t pm)

writel(info->save_sel | info->sel_bit, info->sel_reg);

- if (!allow_clk_stop(info))
- clk_disable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_DISABLE);
}

return 0;
@@ -1072,7 +1100,7 @@ static int s3c24xx_nand_resume(struct platform_device *dev)
unsigned long sel;

if (info) {
- clk_enable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_ENABLE);
s3c2410_nand_inithw(info);

/* Restore the state of the nFCE line. */
@@ -1082,8 +1110,7 @@ static int s3c24xx_nand_resume(struct platform_device *dev)
sel |= info->save_sel & info->sel_bit;
writel(sel, info->sel_reg);

- if (allow_clk_stop(info))
- clk_disable(info->clk);
+ s3c2410_nand_clk_set_state(info, CLOCK_SUSPEND);
}

return 0;
--
1.7.4.4


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