From patchwork Thu Mar 28 16:35:16 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Philipp Zabel X-Patchwork-Id: 2358051 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id A1A23DF2A1 for ; Thu, 28 Mar 2013 16:36:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756215Ab3C1QgE (ORCPT ); Thu, 28 Mar 2013 12:36:04 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:56954 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756504Ab3C1QgD (ORCPT ); Thu, 28 Mar 2013 12:36:03 -0400 Received: from pizza.hi.pengutronix.de ([10.1.0.104] helo=pizza.pengutronix.de) by metis.ext.pengutronix.de with esmtp (Exim 4.72) (envelope-from ) id 1ULFnl-0007E1-Mp; Thu, 28 Mar 2013 17:35:45 +0100 From: Philipp Zabel To: linux-arm-kernel@lists.infradead.org, Arnd Bergmann Cc: Greg Kroah-Hartman , Stephen Warren , Marek Vasut , Fabio Estevam , Sascha Hauer , Shawn Guo , kernel@pengutronix.de, devicetree-discuss@lists.ozlabs.org, Mike Turquette , Len Brown , Pavel Machek , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, Stephen Warren , Philipp Zabel Subject: [PATCH v6 1/8] dt: describe base reset signal binding Date: Thu, 28 Mar 2013 17:35:16 +0100 Message-Id: <1364488523-20310-2-git-send-email-p.zabel@pengutronix.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1364488523-20310-1-git-send-email-p.zabel@pengutronix.de> References: <1364488523-20310-1-git-send-email-p.zabel@pengutronix.de> X-SA-Exim-Connect-IP: 10.1.0.104 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-pm@vger.kernel.org Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: Stephen Warren This binding is intended to represent the hardware reset signals present internally in most IC (SoC, FPGA, ...) designs. It consists of a binding for a reset controller device (provider), and a pair of properties, "resets" and "reset-names", to link a device node (consumer) to its reset controller via phandle, similarly to the clock and interrupt bindings. The reset controller has all information necessary to reset the consumer device. That could be provided via device tree, or it could be implemented in hardware. The aim is to enable device drivers to request a framework API to issue a reset simply by providing their struct device pointer as the most common case. Signed-off-by: Stephen Warren Signed-off-by: Philipp Zabel Reviewed-by: Shawn Guo Reviewed-by: Marek Vasut Acked-by: Rob Herring --- Documentation/devicetree/bindings/reset/reset.txt | 75 +++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 Documentation/devicetree/bindings/reset/reset.txt diff --git a/Documentation/devicetree/bindings/reset/reset.txt b/Documentation/devicetree/bindings/reset/reset.txt new file mode 100644 index 0000000..31db6ff --- /dev/null +++ b/Documentation/devicetree/bindings/reset/reset.txt @@ -0,0 +1,75 @@ += Reset Signal Device Tree Bindings = + +This binding is intended to represent the hardware reset signals present +internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole +standalone chips are most likely better represented as GPIOs, although there +are likely to be exceptions to this rule. + +Hardware blocks typically receive a reset signal. This signal is generated by +a reset provider (e.g. power management or clock module) and received by a +reset consumer (the module being reset, or a module managing when a sub- +ordinate module is reset). This binding exists to represent the provider and +consumer, and provide a way to couple the two together. + +A reset signal is represented by the phandle of the provider, plus a reset +specifier - a list of DT cells that represents the reset signal within the +provider. The length (number of cells) and semantics of the reset specifier +are dictated by the binding of the reset provider, although common schemes +are described below. + +A word on where to place reset signal consumers in device tree: It is possible +in hardware for a reset signal to affect multiple logically separate HW blocks +at once. In this case, it would be unwise to represent this reset signal in +the DT node of each affected HW block, since if activated, an unrelated block +may be reset. Instead, reset signals should be represented in the DT node +where it makes most sense to control it; this may be a bus node if all +children of the bus are affected by the reset signal, or an individual HW +block node for dedicated reset signals. The intent of this binding is to give +appropriate software access to the reset signals in order to manage the HW, +rather than to slavishly enumerate the reset signal that affects each HW +block. + += Reset providers = + +Required properties: +#reset-cells: Number of cells in a reset specifier; Typically 0 for nodes + with a single reset output and 1 for nodes with multiple + reset outputs. + +For example: + + rst: reset-controller { + #reset-cells = <1>; + }; + += Reset consumers = + +Required properties: +resets: List of phandle and reset specifier pairs, one pair + for each reset signal that affects the device, or that the + device manages. Note: if the reset provider specifies '0' for + #reset-cells, then only the phandle portion of the pair will + appear. + +Optional properties: +reset-names: List of reset signal name strings sorted in the same order as + the resets property. Consumers drivers will use reset-names to + match reset signal names with reset specifiers. + +For example: + + device { + resets = <&rst 20>; + reset-names = "reset"; + }; + +This represents a device with a single reset signal named "reset". + + bus { + resets = <&rst 10> <&rst 11> <&rst 12> <&rst 11>; + reset-names = "i2s1", "i2s2", "dma", "mixer"; + }; + +This represents a bus that controls the reset signal of each of four sub- +ordinate devices. Consider for example a bus that fails to operate unless no +child device has reset asserted.