Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753572AbbDGSou (ORCPT ); Tue, 7 Apr 2015 14:44:50 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:36453 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753447AbbDGSoN (ORCPT ); Tue, 7 Apr 2015 14:44:13 -0400 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, geert@linux-m68k.org Subject: [PATCH v6 4/4] clk: dt: Introduce binding for always-on clock support Date: Tue, 7 Apr 2015 19:43:59 +0100 Message-Id: <1428432239-4114-5-git-send-email-lee.jones@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1428432239-4114-1-git-send-email-lee.jones@linaro.org> References: <1428432239-4114-1-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: 2704 Lines: 62 Signed-off-by: Lee Jones --- .../devicetree/bindings/clock/clock-bindings.txt | 38 ++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 06fc6d5..daf3323 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -44,6 +44,44 @@ 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. + + 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 an always-on clock. + +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 -- 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/