Re: Using loader to switch kernel and root device on Pi2

ob prohaska <fbsd_at_www.zefox.net> wrote on
Date: Thu, 03 Apr 2025 16:07:30 UTC :

> On Wed, Apr 02, 2025 at 06:57:23PM -0600, Warner Losh wrote:
> > 
> > No. Loader.env is EFI specific and read super early in the setup so you can
> > change the loaddev or currdev.
> 
> Is it early enough to influence the behavior of u-boot? I'm looking to 
> add a delay of a few seconds for mechanical disk detection. There was
> a config.txt variable usb_pgood_delay for that purpose, but it's gone
> from the documentation AFAICT.


https://github.com/u-boot/u-boot/blob/master/common/usb_hub.c

has in usb_hub_power_on(. . .):

. . .
	unsigned pgood_delay = hub->desc.bPwrOn2PwrGood * 2;

	. . .

	/*
	 * Wait for power to become stable,
	 * plus spec-defined max time for device to connect
	 * but allow this time to be increased via env variable as some
	 * devices break the spec and require longer warm-up times
	 */
#if CONFIG_IS_ENABLED(ENV_SUPPORT)
	env = env_get("usb_pgood_delay");
	if (env)
		pgood_delay = max(pgood_delay,
			          (unsigned)simple_strtol(env, NULL, 0));
#endif
	debug("pgood_delay=%dms\n", pgood_delay);

	/*
	 * Do a minimum delay of the larger value of 100ms or pgood_delay
	 * so that the power can stablize before the devices are queried
	 */
	hub->query_delay = get_timer(0) + max(100, (int)pgood_delay);

	/*
	 * Record the power-on timeout here. The max. delay (timeout)
	 * will be done based on this value in the USB port loop in
	 * usb_hub_configure() later.
	 */
	hub->connect_timeout = hub->query_delay + HUB_DEBOUNCE_TIMEOUT;
	debug("devnum=%d poweron: query_delay=%d connect_timeout=%d\n",
	      dev->devnum, max(100, (int)pgood_delay),
	      max(100, (int)pgood_delay) + HUB_DEBOUNCE_TIMEOUT);


So CONFIG_IS_ENABLED(ENV_SUPPORT) is required to be able to
override the default value involved. I've not checked if the
FreeBSD U-Boot ports are enabling that or not.


===
Mark Millard
marklmi at yahoo.com