linux-kernel - Re: [PATCH v3 03/13] PM / Domains: Add DT bindings for PM QoS device latencies

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Date:	Fri, 26 Sep 2014 10:28:48 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Geert Uytterhoeven <geert+renesas@...der.be>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Philipp Zabel <philipp.zabel@...il.com>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 03/13] PM / Domains: Add DT bindings for PM QoS device latencies

On 25 September 2014 18:28, Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> PM QoS device start/stop and save/restore state latencies are more or
> less properties of the hardware.
> In legacy code, they're specified from platform code.
> On DT platforms, their values should come from DT.

I am not so sure about this.

First, I think there a too much software affecting these latencies to
call them hardware properties.

Second, I am not sure that the future version of genpd will have all
these four latencies, but maybe only two. Let's see. I would thus
suggest to put this patch on hold for a while.

Kind regards
Uffe

>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> Should these properties be called "linux,*-latency"?
>
> v3:
>   - No changes
> v2:
>   - New
>
>  Documentation/devicetree/bindings/power/power_domain.txt | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/power/power_domain.txt b/Documentation/devicetree/bindings/power/power_domain.txt
> index 7bc421d84367d636..024815bc257723b1 100644
> --- a/Documentation/devicetree/bindings/power/power_domain.txt
> +++ b/Documentation/devicetree/bindings/power/power_domain.txt
> @@ -42,12 +42,22 @@ Required properties:
>   - power-domains : A phandle and PM domain specifier as defined by bindings of
>                     the power controller specified by phandle.
>
> +Optional properties:
> + - stop-latency: Stop latency of the device, in ns,
> + - start-latency: Start latency of the device, in ns,
> + - save-state-latency: Save-state latency of the device, in ns,
> + - restore-state-latency: Restore-state latency of the device, in ns.
> +
>  Example:
>
>         leaky-device@...50000 {
>                 compatible = "foo,i-leak-current";
>                 reg = <0x12350000 0x1000>;
>                 power-domains = <&power 0>;
> +               stop-latency = <250000>;
> +               start-latency = <250000>;
> +               save-state-latency = <250000>;
> +               restore-state-latency = <250000>;
>         };
>
>  The node above defines a typical PM domain consumer device, which is located
> --
> 1.9.1
>
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