Re: [PATCH v2.6.34-rc2] s3c: Fix CONFIG_MTD_NAND_S3C2410_CLKSTOP

[Ben Dooks <ben-linux@fluff.org>]

On Tue, Mar 30, 2010 at 10:22:03AM +0200, Christian Pellegrin wrote:
> Option CONFIG_MTD_NAND_S3C2410_CLKSTOP was broken by higher MTD layers
> calling select_chip with -1 twice in a row. This patch fixes the problem
> by making sure that clk_disable is not called too many times.
> 
> Signed-off-by: Christian Pellegrin <chripell@fsfe.org>
> ---
>  drivers/mtd/nand/s3c2410.c |   10 ++++++++--
>  1 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/s3c2410.c b/drivers/mtd/nand/s3c2410.c
> index fa6e9c7..9adecc6 100644
> --- a/drivers/mtd/nand/s3c2410.c
> +++ b/drivers/mtd/nand/s3c2410.c
> @@ -37,6 +37,7 @@
>  #include <linux/slab.h>
>  #include <linux/clk.h>
>  #include <linux/cpufreq.h>
> +#include <linux/bitops.h>
>  
>  #include <linux/mtd/mtd.h>
>  #include <linux/mtd/nand.h>
> @@ -135,6 +136,9 @@ struct s3c2410_nand_info {
>  #ifdef CONFIG_CPU_FREQ
>  	struct notifier_block	freq_transition;
>  #endif
> +#ifdef CONFIG_MTD_NAND_S3C2410_CLKSTOP
> +	unsigned long                   clk_running;
> +#endif
>  };
>  
>  /* conversion functions */
> @@ -333,7 +337,8 @@ 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))
> +	if (chip != -1 && allow_clk_stop(info) &&
> +	    !test_and_set_bit(0, &info->clk_running))
>  		clk_enable(info->clk);

please let me know why you feel the need to use test_and_set_bit on
a variable that is single use.
  
>  	cur = readl(info->sel_reg);
> @@ -356,7 +361,8 @@ static void s3c2410_nand_select_chip(struct mtd_info *mtd, int chip)
>  
>  	writel(cur, info->sel_reg);
>  
> -	if (chip == -1 && allow_clk_stop(info))
> +	if (chip == -1 && allow_clk_stop(info) &&
> +	    test_and_clear_bit(0, &info->clk_running))
>  		clk_disable(info->clk);
>  }
>  
> -- 
> 1.5.6.5
> 
> --
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-- 
-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.