[PATCH] mtd: nand_mxs: fix NAND error when change clk rate

[Sascha Hauer]

On Wed, Dec 21, 2016 at 10:38:41PM +0100, Christian Hemp wrote:
> The function "nand_enable_edo_mode" changed the NAND clk rate, without turning
> it off. In this case it is posible to get the following errors:
>     MXS NAND: Error sending command
>     MXS NAND: Error sending command
>     MXS NAND: DMA read error
> 
> This can be fixed if the NAND clk is disabled before we change the clk
> rate.
> 
> Tested with:
> nand: NAND device: Manufacturer ID: 0x2c, Chip ID: 0xdc (Micron
> MT29F4G08ABADAWP), 512MiB, page size: 2048, OOB size: 64
> 
> Signed-off-by: Christian Hemp <c.hemp at phytec.de>
> ---
>  drivers/mtd/nand/nand_mxs.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/mtd/nand/nand_mxs.c b/drivers/mtd/nand/nand_mxs.c
> index cba0bee..ce79bca 100644
> --- a/drivers/mtd/nand/nand_mxs.c
> +++ b/drivers/mtd/nand/nand_mxs.c
> @@ -2047,7 +2047,9 @@ static int mxs_nand_enable_edo_mode(struct mxs_nand_info *info)
>  	nand->select_chip(mtd, -1);
>  
>  	/* [3] set the main IO clock, 100MHz for mode 5, 80MHz for mode 4. */
> +	clk_disable(info->clk);
>  	clk_set_rate(info->clk, (mode == 5) ? 100000000 : 80000000);
> +	clk_enable(info->clk);

Calling clk_disable doesn't guarantee that the clock is actually
disabled. If there's another user of the same clock then clk_disable
will only decrease the usage counter.
I think if possible we should fix this in the clock driver instead.

Sascha

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