Re: [RESEND PATCH 2/2] soc: qcom: rpmhpd: Make power_on actually enable the domain

On Thu, 12 Aug 2021 at 15:21, Dmitry Baryshkov
[off-list ref] wrote:

On 03/07/2021 05:54, Bjorn Andersson wrote:

quoted

The general expectation is that powering on a power-domain should make
the power domain deliver some power, and if a specific performace state
is needed further requests has to be made.

But in contrast with other power-domain implementations (e.g. rpmpd) the
RPMh does not have an interface to enable the power, so the driver has
to vote for a particular corner (performance level) in rpmh_power_on().

But the corner is never initialized, so a typical request to simply
enable the power domain would not actually turn on the hardware. Further
more, when no more clients vote for a performance state (i.e. the
aggregated vote is 0) the power domain would be turn off.

Fix both of these issues by always voting for a corner with non-zero
value, when the power domain is enabled.

The tracking of the lowest non-zero corner is performed to handle the
corner case if there's ever a domain with a non-zero lowest corner, in
which case both rpmh_power_on() and rpmh_rpmhpd_set_performance_state()
would be allowed to use this lowest corner.

Fixes: 279b7e8a62cc ("soc: qcom: rpmhpd: Add RPMh power domain driver")
Signed-off-by: Bjorn Andersson <redacted>
---

Resending because the hunk in rpmhpd_update_level_mapping() was left in the
index.

So, colleagues, what is the fate of this patch? Is it going to be
applied? Or we agree that current approach (power_on +
set_performance_state) is the expected behaviour? My patches on gdsc
rework depend on this patch, but I can rework in them in favour of
required-opp approach.

Today, genpd treats performance states and power on/off states as
orthogonal. You know this already, ofcourse.

Although, to clarify, this means that the genpd provider has to deal
with the scenario when its ->set_performance_state() callback may be
invoked, while the PM domain is turned off, for example. Similarly,
genpd may power on the PM domain by invoking the ->power_on()
callback, before the ->set_performance_state() has been invoked. And
finally, the power domain may be turned off even if there are some
active votes for a performance state.

So for now, the genpd provider needs to deal with these cases. Yes, we
have discussed changing the behaviour in genpd around this and I think
there have been some good reasons for it, but we are not there, at
least yet.

[...]

Kind regards
Uffe