Re: [PATCH 1/2] tx4938ide: Check minimum cycle time and SHWT range

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Atsushi Nemoto wrote:

> From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
> Subject: [PATCH] tx4938ide: Check minimum cycle time and SHWT range (v2)
>
> SHWT value is used as address valid to -CSx assertion and -CSx to -DIOx
> assertion setup time, and contrarywise, -DIOx to -CSx release and -CSx
> release to address invalid hold time, so it actualy applies 4 times and
> so constitutes -DIOx recovery time.  Check requirement of the recovery
> time and cycle time.  Also check SHWT maximum value.
>
> Suggested-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
> Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
>   

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>

> diff --git a/drivers/ide/tx4938ide.c b/drivers/ide/tx4938ide.c
> index a0d10a9..796289c 100644
> --- a/drivers/ide/tx4938ide.c
> +++ b/drivers/ide/tx4938ide.c
> @@ -39,10 +39,17 @@ static void tx4938ide_tune_ebusc(unsigned int ebus_ch,
>  	/* Address-valid to DIOR/DIOW setup */
>  	shwt = DIV_ROUND_UP(t->setup, cycle);
>  
> +	/* -DIOx recovery time (SHWT * 4) and cycle time requirement */
> +	while ((shwt * 4 + wt + (wt ? 2 : 3)) * cycle < t->cycle)
>   

   Besides, it's worth making 'wt' variable signed, otherwise you're 
risking underflow when subtracting 2 above...

WBR, Sergei