LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Sibi Sankar <sibis@codeaurora.org>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Andy Gross <agross@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Pavel Machek <pavel@ucw.cz>, Len Brown <len.brown@intel.com>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	Doug Anderson <dianders@chromium.org>,
	linux-kernel-owner@vger.kernel.org,
	Kevin Hilman <khilman@kernel.org>,
	linux-arm-msm-owner@vger.kernel.org
Subject: Re: [PATCH 1/2] PM / Domains: Add GENPD_FLAG_SUSPEND_ON flag
Date: Mon, 17 Aug 2020 22:19:20 +0530
Message-ID: <33169e221707a2456397e478b275cfa9@codeaurora.org> (raw)
In-Reply-To: <CAPDyKFrqxRrWSX5VaMy4DSjFNaMikKBYsZy5NiPMJvUybYttsw@mail.gmail.com>

On 2020-08-17 14:14, Ulf Hansson wrote:
> On Thu, 13 Aug 2020 at 19:26, Sibi Sankar <sibis@codeaurora.org> wrote:
>> 
>> On 2020-08-13 18:04, Ulf Hansson wrote:
>> > On Wed, 12 Aug 2020 at 19:03, Sibi Sankar <sibis@codeaurora.org> wrote:
>> >>
>> >> Uffe,
>> >> Thanks for taking time to review the
>> >> series!
>> >>
>> >> On 2020-08-12 15:15, Ulf Hansson wrote:
>> >> > On Tue, 11 Aug 2020 at 21:03, Sibi Sankar <sibis@codeaurora.org> wrote:
>> >> >>
>> >> >> This is for power domains which needs to stay powered on for suspend
>> >> >> but can be powered on/off as part of runtime PM. This flag is aimed at
>> >> >> power domains coupled to remote processors which enter suspend states
>> >> >> independent to that of the application processor. Such power domains
>> >> >> are turned off only on remote processor crash/shutdown.
>> >> >
>> >> > As Kevin also requested, please elaborate more on the use case.
>> >> >
>> >> > Why exactly must the PM domain stay powered on during system suspend?
>> >> > Is there a wakeup configured that needs to be managed - or is there a
>> >> > co-processor/FW behaviour that needs to be obeyed to?
>> >>
>> >> Yes this is a co-processor behavior that
>> >> needs to be obeyed. Specifically application
>> >> processor notifies the Always on Subsystem
>> >> (AOSS) that a particular co-processor is up
>> >> using the power domains exposed by AOSS QMP
>> >> driver. AOSS uses this information to wait
>> >> for the co-processors to suspend before
>> >> starting its sleep sequence. The application
>> >> processor powers off these power domains only
>> >> if the co-processor has crashed or powered
>> >> off.
>> >
>> > Thanks for clarifying!
>> >
>> > Although, can you please elaborate a bit more on the actual use case?
>> > What are the typical co-processor and what drivers are involved in
>> > managing it?
>> 
>> The co-processors using the power domains
>> exposed by qcom_aoss driver are modem,
>> audio dsp, compute dsp managed using
>> qcom_q6v5_mss and qcom_q6v5_pas driver.
>> 
>> >
>> > As you may know, runtime PM becomes disabled during system suspend of
>> > a device. Which means, if the driver tries to power off the
>> > coprocessor (via calling pm_runtime_put() for example), somewhere in
>> > the system suspend phase of the corresponding device, its attached PM
>> > domain stays powered on when managed by genpd.
>> 
>> The drivers aren't really expected
>> do anything during suspend/resume
>> pretty much because the co-processors
>> enter low-power modes independent to
>> that of the application processor. On
>> co-processor crash the remoteproc core
>> does a pm_stay_awake followed by a
>> pm_relax after crash recovery.
> 
> Okay, thanks again for clarifying. You have convinced me about the
> need for a new flag to cope with these use cases.
> 
> Would you mind updating the commit message with some of the
> information you just provided?
> 
> Additionally, to make it clear that the flag should be used to keep
> the PM domain powered on during system suspend, but only if it's
> already powered on - please rename the flag to GENPD_FLAG_NO_SUSPEND,
> and update the corresponding description of it in the header file.

Thanks, naming it ^^ makes more sense :)

https://lore.kernel.org/lkml/340a7aafcf0301ff3158a4e211992041@codeaurora.org/

Also we wouldn't want to power on
runtime suspended power domains with
the NO_SUSPEND flag set, on resume as
explained ^^. Do you agree with that
as well?

> 
> [...]
> 
> Kind regards
> Uffe

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-11 19:02 Sibi Sankar
2020-08-11 19:02 ` [PATCH 2/2] soc: qcom: aoss: Use " Sibi Sankar
2020-08-11 21:16   ` Doug Anderson
2020-08-11 21:17 ` [PATCH 1/2] PM / Domains: Add " Doug Anderson
2020-08-11 21:38 ` Stephen Boyd
2020-08-12 13:36   ` Sibi Sankar
2020-08-12  0:19 ` Kevin Hilman
2020-08-12 16:12   ` Sibi Sankar
2020-08-12  9:45 ` Ulf Hansson
2020-08-12 17:02   ` Sibi Sankar
2020-08-13 12:34     ` Ulf Hansson
2020-08-13 17:26       ` Sibi Sankar
2020-08-17  8:44         ` Ulf Hansson
2020-08-17 16:49           ` Sibi Sankar [this message]
2020-08-18  8:31             ` Ulf Hansson
2020-08-18  9:03               ` Sibi Sankar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=33169e221707a2456397e478b275cfa9@codeaurora.org \
    --to=sibis@codeaurora.org \
    --cc=agross@kernel.org \
    --cc=bjorn.andersson@linaro.org \
    --cc=dianders@chromium.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=khilman@kernel.org \
    --cc=len.brown@intel.com \
    --cc=linux-arm-msm-owner@vger.kernel.org \
    --cc=linux-arm-msm@vger.kernel.org \
    --cc=linux-kernel-owner@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=pavel@ucw.cz \
    --cc=rjw@rjwysocki.net \
    --cc=rnayak@codeaurora.org \
    --cc=ulf.hansson@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git