From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Ripard Subject: Re: [PATCH v7 5/5] clk: dt: Introduce binding for critical clock support Date: Tue, 28 Jul 2015 11:32:22 +0200 Message-ID: <20150728093222.GV2564@lukather> 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> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="6Jy4/gb9ZgnsEOX8" Return-path: Content-Disposition: inline In-Reply-To: <20150727073149.GV3436@x1> Sender: linux-kernel-owner@vger.kernel.org To: Lee Jones 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 --6Jy4/gb9ZgnsEOX8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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-bindings.t= xt b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > > index 06fc6d5..4137034 100644 > > > --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt > > > +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > > @@ -44,6 +44,45 @@ For example: > > > clocks by index. The names should reflect the clock output signal > > > names for the device. > > > =20 > > > +critical-clock: Some hardware contains bunches of clocks which, in n= ormal > > > + circumstances, must never be turned off. If drivers a) fail to > > > + obtain a reference to any of these or b) give up a previously > > > + obtained reference during suspend, it is possible that some > > > + Operating Systems might attempt to disable them to save power. > > > + If this happens a platform can fail irrecoverably as a result. > > > + 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 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 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. Using > > indices for clocks that don't have any (for example because it only > > 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? What I had in mind was that, you would have three cases: - critical-clocks is not there: no clocks are made critical - critical-clocks is there, but doesn't have any values: all the clocks provided are marked critical - critical-clocks is there and it has a list of values: only the clocks listed are marked critical. Does that make sense to you? Thanks, Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --6Jy4/gb9ZgnsEOX8 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVt0wmAAoJEBx+YmzsjxAgcCYP/jwj+pMRdvkORvlRwhG+unL5 bffXUgEcskccJkg+/AF5KjZwiqKu4QvOs4ENOuZZbq9hz6399kWGuUXgeYYhnFk9 7uCUyJMPsUi5pjh9RAe6VpuDfYJbzcgVVfa/tS5bl78+cr6ZmcybQwiRvyopdJvc ImQTTrjwVwX30BbZRt15Ucnc59OPU2BWOu9w+oX51bneip1deePsW6cORZtvZova cp0XG06jxiGf0g71x7SGjTsIRbjCxsKtipzA/o8lKK3UY8MrJVQYNHRb/aHp39ZA czH9zHV0zY71lnjltLeO0CkCphGbJPVKJnf1aU1aG6XKpfZngDaYhKJxKgc5Y0Sp btOQYnTHAenUPGbloWtzLXOFIEk5PnZAuXKdl1h+p0V9l5Gg1BudL3xaunqNhidE tQg54wPrLKQKV5SGy48Sn2Ra+cXKe0eVp7ColHRrxu0qGO48mV/h1xDRyIRdP5jS E7rf4P0Oh64nLUNpziufKnCtDAgLXA6YFNd/FjKolP3L+y2KWuOM5NYH3WHrzLfk kgqTTfqeIXTNojGDXPAsmM7edEgVn39xxn8B/edELeJqJM8aoSxAGoZ5rWjddDVE acGYhvnqNtFt/317hIu5w1FZC8bNyXMP0GMhdSu7FJFvcX5zF82CGksyF41d29Pp mayll0EH9NAyVpTmTRn+ =Qvin -----END PGP SIGNATURE----- --6Jy4/gb9ZgnsEOX8--