Re: [PATCH 07/18] drivers: firmware: psci: Prepare to use OS initiated suspend mode

From: Sudeep Holla <sudeep.holla@arm.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	"Raju P . L . S . S . S . N" <rplsssn@codeaurora.org>,
	Amit Kucheria <amit.kucheria@linaro.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Niklas Cassel <niklas.cassel@linaro.org>,
	Tony Lindgren <tony@atomide.com>,
	Kevin Hilman <khilman@kernel.org>,
	Lina Iyer <ilina@codeaurora.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Souvik Chakravarty <souvik.chakravarty@arm.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Linux PM <linux-pm@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Lina Iyer <lina.iyer@linaro.org>
Subject: Re: [PATCH 07/18] drivers: firmware: psci: Prepare to use OS initiated suspend mode
Date: Mon, 10 Jun 2019 11:42:53 +0100	[thread overview]
Message-ID: <20190610104253.GB26602@e107155-lin> (raw)
In-Reply-To: <CAPDyKFoKNLqLzVx8uj_-iuWAHGCvty28mVKnipFVgjKD8oDNkQ@mail.gmail.com>

On Mon, Jun 10, 2019 at 12:21:10PM +0200, Ulf Hansson wrote:
> On Fri, 7 Jun 2019 at 17:17, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > On Mon, May 13, 2019 at 09:22:49PM +0200, Ulf Hansson wrote:
> > > The per CPU variable psci_power_state, contains an array of fixed values,
> > > which reflects the corresponding arm,psci-suspend-param parsed from DT, for
> > > each of the available CPU idle states.
> > >
> > > This isn't sufficient when using the hierarchical CPU topology in DT in
> > > combination with having PSCI OS initiated (OSI) mode enabled. More
> > > precisely, in OSI mode, Linux is responsible of telling the PSCI FW what
> > > idle state the cluster (a group of CPUs) should enter, while in PSCI
> > > Platform Coordinated (PC) mode, each CPU independently votes for an idle
> > > state of the cluster.
> > >
> > > For this reason, let's introduce an additional per CPU variable called
> > > domain_state and implement two helper functions to read/write its values.
> > > Following patches, which implements PM domain support for PSCI, will use
> > > the domain_state variable and set it to corresponding bits that represents
> > > the selected idle state for the cluster.
> > >
> > > Finally, in psci_cpu_suspend_enter() and psci_suspend_finisher(), let's
> > > take into account the values in the domain_state, as to get the complete
> > > suspend parameter.
> > >
> >
> > I understand it was split to ease review, but this patch also does
> > nothing as domain_state = 0 always. I was trying hard to find where it's
> > set, but I assume it will be done in later patches. Again may be this
> > can be squashed into the first caller of psci_set_domain_state
> 
> You have a point, but I am worried that it would look like this series
> is solely needed to support OSI mode. This is not the case. Let me
> explain.
> 
> Having $subject patch separate shows the specific changes needed to
> support OSI mode. The first caller of psci_set_domain_state() is added
> in patch9, however, patch9 is useful no matter of OSI or PC mode.
> 
> Moreover, if I squash $subject patch with patch9, I would have to
> squash also the subsequent patch (patch8), as it depends on $subject
> patch.
> 
> So, to conclude, are you happy with this as is or do you want me to
> squash the patches?
> 

Yes I am fine either way. As I put the comments in the same flow as I
did review, I thought it's worth mentioning if someone else get similar
thoughts. I am fine if you prefer to keep it the same way unless someone
else raise the same point.

--
Regards,
Sudeep