[PATCH v3 1/5] reset: Add reset_reset() and reset_reset_bulk() API

[Maarten Brock]

Hello Michal,

> From: Michal Simek <michal.simek at amd.com>
> On 5/18/26 14:07, Maarten Brock wrote:
> >> From: Michal Simek <michal.simek at amd.com>
> >> On 5/18/26 12:21, Maarten Brock wrote:
> >>
> >> I expect you would like to do it like this right?
> >>
> >> int reset_reset_bulk(struct reset_ctl_bulk *bulk, ulong delay_us)
> >> {
> >> 	int ret;
> >>
> >> 	ret = reset_assert_bulk(bulk);
> >> 	if (ret) {
> >> 		dev_err(bus, "Failed to assert reset: %d\n", ret);
> >> 		return ret;
> >> 	}
> >>
> >> 	udelay(delay_us);
> >>
> >> 	/* Deassert all OSPI reset lines */
> >> 	ret = reset_deassert_bulk(bulk);
> >> 	if (ret) {
> >> 		dev_err(bus, "Failed to deassert reset: %d\n", ret);
> >> 		return ret;
> >> 	}
> >>
> >> 	return 0;
> >> }
> >
> > That is correct.
> > And a single delay of delay_us takes less time than N*delay_us (for N>1), so the total startup time is smaller (a.k.a. faster startup).
> 
> It really depends on other factors and delay time. In our case it is not just
> MMIO access. But it is SMC to TF-A and then seconding request over mailbox to
> another firmware to ack it first and then do it. And with above you would have
> to do twice compare to once.
> 
> I can do another optimization which is that if bulk->count is 1 then call
> reset_reset() directly and for others do what you see above.
> 
> What do you think?

I very much doubt that all sorts of actions and compares will ever take more time than 1 us, unless some serial protocol is involved (uart/spi/i2c).
So, I expect that delay_us is always the dominant elapsed time. And N*delay_us even more so.

I do understand that if the delay is handled by rst_reset() and underlying hardware, things might be different.
So special handling of bulk->count=1 or *all* bulk resets are handled by rst_reset() could be a good idea.

How about something like this?

int reset_reset_bulk(struct reset_ctl_bulk *bulk, ulong delay_us)
{
	int i, ret, soft = 0;

	for (i = 0; i < bulk->count; i++) {
		struct reset_ops *ops = reset_dev_ops(bulk->resets[i].dev);

		if (ops->rst_reset) {
			ret = ops->rst_reset(&bulk->resets[i], delay_us);
		} else {
			ret = reset_assert(&bulk->resets[i]);
			soft++;
		}
		if (ret < 0)
			return ret;
	}

	if (soft == 0)
		return 0;

	udelay(delay_us);

	for (i = 0; i < bulk->count; i++) {
		struct reset_ops *ops = reset_dev_ops(bulk->resets[i].dev);

		if (!ops->rst_reset) {
			ret = reset_deassert(&bulk->resets[i]);
			if (ret < 0)
				return ret;
		}
	}

	return 0;
}

Kind regards,
Maarten Brock