From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [PATCH v5 4/4] clk: dt: Introduce binding for always-on clock support Date: Tue, 7 Apr 2015 10:42:23 +0100 Message-ID: <20150407094223.GI3461@x1> References: <1427891304-20160-1-git-send-email-lee.jones@linaro.org> <1427891304-20160-5-git-send-email-lee.jones@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Geert Uytterhoeven Cc: "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , kernel-F5mvAk5X5gdBDgjK7y7TUQ@public.gmane.org, Mike Turquette , Stephen Boyd , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On Thu, 02 Apr 2015, Geert Uytterhoeven wrote: > On Wed, Apr 1, 2015 at 2:28 PM, Lee Jones wrot= e: > > Signed-off-by: Lee Jones > > --- > > .../devicetree/bindings/clock/clock-bindings.txt | 31 ++++++++++= ++++++++++++ > > 1 file changed, 31 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/clock/clock-bindings= =2Etxt b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > index 06fc6d5..94cdda2 100644 > > --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt > > +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > @@ -44,6 +44,37 @@ For example: > > clocks by index. The names should reflect the clock output signa= l > > names for the device. > > > > +clock-always-on: Some hardware contains bunches of clocks which= must never be > > + turned off. If drivers a) fail to obtain a ref= erence to any > > + of these or b) give up a previously obtained re= ference > > + during suspend, the common clk framework will a= ttempt to > > + disable them and a platform can fail irrecovera= bly as a > > + result. Usually the only way to recover from t= hese failures > > + is to reboot. > > + > > + To avoid either of these two scenarios from cat= astrophically > > + disabling an otherwise perfectly healthy runnin= g system, > > + clocks can be identified as always-on using thi= s property > > + from inside a clocksource's node. > > + > > + This property is not to be abused. It is only = to be used to > > + protect platforms from being crippled by gated = clocks, not > > + as a convenience function to avoid using the fr= amework > > + correctly inside device drivers. >=20 > Please document what are the expected value(s) for this property. > I assume these are clock indices into the array of hardware clocks? >=20 > Do they take into account sparse hardware clocks, cfr. the "clock-ind= ices" > property below (I didn't check)? They must match a valid indices. If the clock-indices property is present, the value identified as always-on must match one of the clocks listed. I'll mention that. > > +For example: > > + > > + oscillator { > > + #clock-cells =3D <1>; > > + clock-output-names =3D "ckil", "ckih"; > > + clock-always-on =3D <0>, <1>; > > + }; > > + > > +- this node defines a device with two clock outputs, just as in th= e > > + example above. The only difference being that 'ckil' and 'ckih' > > + are now identified as an always-on clocks, so the framework will > > + know to never attempt to gate them. > > + > > clock-indices: If the identifying number for the clocks in the = node > > is not linear from zero, then this allows the ma= pping of > > identifiers into the clock-output-names array. >=20 > Gr{oetje,eeting}s, >=20 > Geert >=20 --=20 Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org =E2=94=82 Open source software for ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html