From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [PATCH v7 5/5] clk: dt: Introduce binding for critical clock support Date: Thu, 30 Jul 2015 10:23:41 +0100 Message-ID: <20150730092341.GC14642@x1> References: <1437570255-21049-1-git-send-email-lee.jones@linaro.org> <1437570255-21049-6-git-send-email-lee.jones@linaro.org> <20150727071013.GO2564@lukather> <20150727073149.GV3436@x1> <20150728093222.GV2564@lukather> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20150728093222.GV2564@lukather> Sender: linux-kernel-owner@vger.kernel.org To: Maxime Ripard Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel@stlinux.com, mturquette@linaro.org, sboyd@codeaurora.org, devicetree@vger.kernel.org, geert@linux-m68k.org, s.hauer@pengutronix.de List-Id: devicetree@vger.kernel.org On Tue, 28 Jul 2015, Maxime Ripard wrote: > On Mon, Jul 27, 2015 at 08:31:49AM +0100, Lee Jones wrote: > > On Mon, 27 Jul 2015, Maxime Ripard wrote: > >=20 > > > Hi Lee, > > >=20 > > > On Wed, Jul 22, 2015 at 02:04:15PM +0100, Lee Jones wrote: > > > > Signed-off-by: Lee Jones > > > > --- > > > > .../devicetree/bindings/clock/clock-bindings.txt | 39 ++++++= ++++++++++++++++ > > > > 1 file changed, 39 insertions(+) > > > >=20 > > > > diff --git a/Documentation/devicetree/bindings/clock/clock-bind= ings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > > > index 06fc6d5..4137034 100644 > > > > --- a/Documentation/devicetree/bindings/clock/clock-bindings.tx= t > > > > +++ b/Documentation/devicetree/bindings/clock/clock-bindings.tx= t > > > > @@ -44,6 +44,45 @@ For example: > > > > clocks by index. The names should reflect the clock output s= ignal > > > > names for the device. > > > > =20 > > > > +critical-clock: Some hardware contains bunches of clocks which= , in normal > > > > + circumstances, must never be turned off. If drivers a) fail= to > > > > + obtain a reference to any of these or b) give up a previousl= y > > > > + obtained reference during suspend, it is possible that some > > > > + Operating Systems might attempt to disable them to save powe= r. > > > > + If this happens a platform can fail irrecoverably as a resul= t. > > > > + Usually the only way to recover from these failures is to > > > > + reboot. > > > > + > > > > + To avoid either of these two scenarios from catastrophically > > > > + disabling an otherwise perfectly healthy running system, > > > > + clocks can be identified as 'critical' using this property f= rom > > > > + 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 a= s a > > > > + convenience function to avoid using the framework correctly > > > > + inside device drivers. > > > > + > > > > + Expected values are hardware clock indices. If the > > > > + clock-indices property (see below) is used, then supplied > > > > + values must correspond to one of the listed identifiers. > > > > + Using the clock-indices example below, hardware clock <2> > > > > + is missing, therefore it is considered invalid to then > > > > + list clock <2> as a critical clock. > > >=20 > > > I think we should also consider having it simply as a boolean. Us= ing > > > indices for clocks that don't have any (for example because it on= ly > > > provides a single clock) seem to not really make much sense. > >=20 > > Then how would you distinguish between the clocks if the provider > > provides more than a single clock? >=20 > What I had in mind was that, you would have three cases: >=20 > - critical-clocks is not there: no clocks are made critical >=20 > - critical-clocks is there, but doesn't have any values: all the > clocks provided are marked critical >=20 > - critical-clocks is there and it has a list of values: only the > clocks listed are marked critical. >=20 > Does that make sense to you? Yep, sounds good. --=20 Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org =E2=94=82 Open source software for ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog