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Date:   Thu, 31 May 2018 14:44:10 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>, 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>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Kevin Hilman <khilman@kernel.org>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-tegra@vger.kernel.org
Subject: Re: [PATCH v2 0/9] PM / Domains: Add support for multi PM domains
 per device
Message-ID: <20180531091410.fl5f42zmyqi6zj5a@vireshk-i7>
References: <20180529100421.31022-1-ulf.hansson@linaro.org>
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On 29-05-18, 12:04, Ulf Hansson 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!

Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh