From mboxrd@z Thu Jan 1 00:00:00 1970 From: lee.jones@linaro.org (Lee Jones) Date: Wed, 1 Apr 2015 13:28:24 +0100 Subject: [PATCH v5 4/4] clk: dt: Introduce binding for always-on clock support In-Reply-To: <1427891304-20160-1-git-send-email-lee.jones@linaro.org> References: <1427891304-20160-1-git-send-email-lee.jones@linaro.org> Message-ID: <1427891304-20160-5-git-send-email-lee.jones@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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.txt 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 signal 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 reference to any + of these or b) give up a previously obtained reference + during suspend, the common clk framework will attempt to + disable them and 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 always-on 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. + +For example: + + oscillator { + #clock-cells = <1>; + clock-output-names = "ckil", "ckih"; + clock-always-on = <0>, <1>; + }; + +- this node defines a device with two clock outputs, just as in the + 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 mapping of identifiers into the clock-output-names array. -- 1.9.1