suspend/resume timings

[Jim Gettys]

The keyboard is left powered up during suspend: we shouldn't need to
reset it at all (except on power up).  This is so you can touch a key or
the keypad and get the CPU back instanty.
                             - Jim


On Sun, 2007-04-01 at 21:09 +0200, Jens Axboe wrote:
> Hi,
> 
> I took a look at the time spent doing a suspend and resume cycle. In
> general things go pretty fast, most devices handle it really quickly.
> USB is a bit slow (~100 msec), but I ignored that since apparently there
> are already people working on fixing USB suspend (functionality, speed
> of course comes second).
> 
> The slowest parts are the keyboard and mouse. psmouse takes ~570 msec to
> resume alone, and the keyboard is no speed daemon at ~269 msecs. Looking
> at the psmouse first, by far the majority of the time is spend resetting
> the device (drivers/input/mouse/olpc.c:olpc_reconnect() ->
> psmouse_reset()). A quick test works fine for me without the reset, but
> that may not be a sound approach. Perhaps deferring a reset to IFF
> olpc_get_model() fails would be more safe?
> 
> I'll be playing some more with the timings and testing over the next
> week, do let me know if there's something more urgent in suspend/resume
> area that needs attention.
> 
> The kernel used was current olpc-2.6.
> 
> diff --git a/drivers/input/mouse/olpc.c b/drivers/input/mouse/olpc.c
> index 5f813f5..d2df132 100644
> --- a/drivers/input/mouse/olpc.c
> +++ b/drivers/input/mouse/olpc.c
> @@ -351,12 +351,19 @@ static int olpc_poll(struct psmouse *psmouse)
>  static int olpc_reconnect(struct psmouse *psmouse)
>  {
>  	struct olpc_data *priv = psmouse->private;
> +	struct olpc_model_info *info;
>  	int mode;
>  
> -	psmouse_reset(psmouse);
> -
> -	if (!(priv->i = olpc_get_model(psmouse)))
> -		return -1;
> +	/*
> +	 * defer reset to if olpc_get_model() fails, it's quite a time eater
> +	 */
> +	priv->i = olpc_get_model(psmouse);
> +	if (!priv->i) {
> +		psmouse_reset(psmouse);
> +		priv->i = olpc_get_model(psmouse);
> +		if (!priv->i)
> +			return -1;
> +	}
>  
>  	mode = olpc_find_mode(psmouse);
>  	if (mode < 0)
> 
-- 
Jim Gettys
One Laptop Per Child