Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755461AbbB0VXH (ORCPT ); Fri, 27 Feb 2015 16:23:07 -0500 Received: from mail-wi0-f171.google.com ([209.85.212.171]:38409 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755393AbbB0VWx (ORCPT ); Fri, 27 Feb 2015 16:22:53 -0500 From: Lee Jones To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: lee.jones@linaro.org, kernel@stlinux.com, mturquette@linaro.org, sboyd@codeaurora.org, devicetree@vger.kernel.org Subject: [PATCH 4/4] clk: dt: Introduce binding for always-on clock support Date: Fri, 27 Feb 2015 21:14:34 +0000 Message-Id: <1425071674-16995-5-git-send-email-lee.jones@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1425071674-16995-1-git-send-email-lee.jones@linaro.org> References: <1425071674-16995-1-git-send-email-lee.jones@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2497 Lines: 58 Signed-off-by: Lee Jones --- .../devicetree/bindings/clock/clock-bindings.txt | 34 ++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 06fc6d5..ad17121 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -44,6 +44,40 @@ 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. The CLK_IGNORE_UNUSED + flag will be applied to each clock instance named in this + property, thus preventing them from being shut down by the + framework. + + 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 = "ckil"; + }; + +- this node defines a device with two clock outputs, just as in the + example above. The only difference being that 'ckil' is now + identified as an always-on clock, so the framework will know to + never attempt to gate it. + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/