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From: Ulf Hansson <ulf.hansson@linaro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
	Andy Gross <agross@kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RESEND PATCH 2/2] soc: qcom: rpmhpd: Make power_on actually enable the domain
Date: Fri, 13 Aug 2021 11:45:54 +0200	[thread overview]
Message-ID: <CAPDyKFoxbm5ki5z0NcbcpJ6bbFntitYTiwX0Bxe01NaB6Db3uQ@mail.gmail.com> (raw)
In-Reply-To: <45bfb6ae-d131-10d7-1924-48c98a957667@linaro.org>

On Thu, 12 Aug 2021 at 15:21, Dmitry Baryshkov
<dmitry.baryshkov@linaro.org> wrote:
>
> On 03/07/2021 05:54, Bjorn Andersson wrote:
> > 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 <bjorn.andersson@linaro.org>
> > ---
> >
> > 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

  reply	other threads:[~2021-08-13  9:46 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-03  0:54 [PATCH 0/2] soc: qcom: rpmhpd: Improve rpmhpd enable handling Bjorn Andersson
2021-07-03  0:54 ` [PATCH 1/2] soc: qcom: rpmhpd: Use corner in power_off Bjorn Andersson
2021-07-05  4:26   ` Rajendra Nayak
2021-07-05  5:06     ` Bjorn Andersson
2021-07-05  5:40       ` Rajendra Nayak
2021-07-07  4:49         ` Bjorn Andersson
2021-07-07  6:31           ` Rajendra Nayak
2021-07-07 15:48             ` Bjorn Andersson
2021-07-07 16:58               ` Dmitry Baryshkov
2021-07-08  0:21   ` Stephen Boyd
2021-07-08  4:35     ` Bjorn Andersson
2021-07-08  5:03       ` Rajendra Nayak
2021-07-08  6:51         ` Stephen Boyd
2021-07-15 10:40   ` Sibi Sankar
2021-07-03  0:54 ` [PATCH 2/2] soc: qcom: rpmhpd: Make power_on actually enable the domain Bjorn Andersson
2021-07-03  2:54   ` [RESEND PATCH " Bjorn Andersson
2021-07-08  0:23     ` Stephen Boyd
2021-07-08  0:25     ` Stephen Boyd
2021-07-14  9:22     ` Rajendra Nayak
2021-07-15 12:16     ` Sibi Sankar
2021-07-15 12:24       ` Rajendra Nayak
2021-08-12 13:21     ` Dmitry Baryshkov
2021-08-13  9:45       ` Ulf Hansson [this message]
2021-07-05 12:55 ` [PATCH 0/2] soc: qcom: rpmhpd: Improve rpmhpd enable handling Ulf Hansson

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