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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 30 May 2018 11:30:33 +0200
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Subject: Re: [PATCH v2 0/9] PM / Domains: Add support for multi PM domains per device
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jon Hunter <jonathanh@nvidia.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Todor Tomov <todor.tomov@linaro.org>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Kevin Hilman <khilman@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-tegra@vger.kernel.org
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On Tue, May 29, 2018 at 12:04 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> Changes in v2:
>         - Addressed comments from Geert around DT doc.
>         - Addressed comments from Jon around clarification of how to use this
>         and changes to returned error codes.
>         - Fixed build error in case CONFIG_PM was unset.
>
> There are devices that are partitioned across multiple PM domains. Currently
> these can't be supported well by the available PM infrastructures we have in
> the kernel. This series is an attempt to address this.
>
> The interesting parts happens from patch 5 an onwards, including a minor DT
> update to the existing power-domain bindings, the 4 earlier are just trivial
> clean-ups of some related code in genpd, which I happened to stumble over.
>
> Some additional background:
>
> One existing case where devices are partitioned across multiple PM domains, is
> the Nvida Tegra 124/210 X-USB subsystem. A while ago Jon Hunter (Nvidia) sent a
> series, trying to address these issues, however this is a new approach, while
> it re-uses the same concepts from DT point of view.
>
> The Tegra 124/210 X-USB subsystem contains of a host controller and a device
> controller. Each controller have its own independent PM domain, but are being
> partitioned across another shared PM domain for the USB super-speed logic.
>
> Currently to make the drivers work, either the related PM domains needs to stay
> powered on always or the PM domain topology needs to be in-correctly modelled
> through sub-domains. In both cases PM domains may be powered on while they
> don't need to be, so in the end this means - wasting power -.
>
> As stated above, this series intends to address these problem from a PM
> infrastructure point of view. More details are available in each changelog.
>
> It should be noted that this series has been tested on HW, however only by using
> a home-cooked test PM domain driver for genpd and together with a test driver.
> This allowed me to play with PM domain (genpd), runtime PM and device links.
>
> Any further deployment for real use cases are greatly appreciated. I am happy to
> to help, if needed!
>
> Kind regards
> Ulf Hansson
>
>
> Ulf Hansson (9):
>   PM / Domains: Drop extern declarations of functions in pm_domain.h
>   PM / Domains: Drop __pm_genpd_add_device()
>   PM / Domains: Drop genpd as in-param for pm_genpd_remove_device()
>   PM / Domains: Drop unused parameter in genpd_allocate_dev_data()
>   PM / Domains: dt: Allow power-domain property to be a list of
>     specifiers
>   PM / Domains: Don't attach devices in genpd with multi PM domains
>   PM / Domains: Split genpd_dev_pm_attach()
>   PM / Domains: Add support for multi PM domains per device to genpd
>   PM / Domains: Add dev_pm_domain_attach_by_id() to manage multi PM
>     domains
>
>  .../bindings/power/power_domain.txt           |  19 ++-
>  drivers/base/power/common.c                   |  39 ++++-
>  drivers/base/power/domain.c                   | 155 ++++++++++++++----
>  drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c       |   2 +-
>  include/linux/pm_domain.h                     |  79 ++++-----
>  5 files changed, 216 insertions(+), 78 deletions(-)

I can take patches [1-4/9] from this series for 4.18.

I need an ACK from Rob on the bindings change.

The rest of the series doesn't seem to be ready yet.

Thanks,
Rafael