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

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

Hello.

Atsushi Nemoto wrote:

> 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>

> diff --git a/drivers/ide/tx4938ide.c b/drivers/ide/tx4938ide.c
> index fa660f9..7e4820e 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 * cycle * 4 + t->act8b < t->cycle)

    This can lead to adding an extra setup cycle due to use of "non-quantized" 
active time, here's more precise expression for the cycle time:

    (shwt * 4 + wt + (wt ? 2 : 3)) * cycle

or even this, more obsure:

    (shwt * 4 + wt + !wt + 2) * cycle

MBR, Sergei