From patchwork Sat Dec 16 10:44:13 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans Verkuil X-Patchwork-Id: 849498 Return-Path: X-Original-To: incoming-dt@patchwork.ozlabs.org Delivered-To: patchwork-incoming-dt@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=devicetree-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3yzP763qy5z9t34 for ; Sat, 16 Dec 2017 21:44:18 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752834AbdLPKoQ (ORCPT ); Sat, 16 Dec 2017 05:44:16 -0500 Received: from lb2-smtp-cloud9.xs4all.net ([194.109.24.26]:35459 "EHLO lb2-smtp-cloud9.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752535AbdLPKoP (ORCPT ); Sat, 16 Dec 2017 05:44:15 -0500 Received: from [192.168.1.10] ([80.101.105.217]) by smtp-cloud9.xs4all.net with ESMTPA id Q9wzelRu4nIXbQ9x0eGR8O; Sat, 16 Dec 2017 11:44:14 +0100 To: Linux Media Mailing List , linux-devicetree From: Hans Verkuil Subject: [PATCH for v4.15] dt-bindings/media/cec-gpio.txt: mention the CEC/HPD max voltages Message-ID: <064113a5-f8be-5b10-091f-a89b87baa5a3@xs4all.nl> Date: Sat, 16 Dec 2017 11:44:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 X-CMAE-Envelope: MS4wfGFGvnYwlmG/eWkMDcGnsZng1gvYC/9cUViuVhTiVQYC11Kc5xLh2UME28/n8Apqgeq/6c0cvVMTf4ss+T8Y+vIfVpkNnJQMcQlU9pIjMlNYvh/Novy/ GtButp+kJk3YQ4T6/Y3RiR9PW5QoSGLMowpNaF0Ck4rX/duDj8Ii2A+t+84/rlUPeihuAr5qCEEYSbHJX7UXlF/QAHCPt9aTxPWsz6uvGhqjt5Li/uN3Pd0o Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Mention the maximum voltages of the CEC and HPD lines. Since in the example these lines are connected to a Raspberry Pi and the Rpi GPIO lines are 3.3V it is a good idea to warn against directly connecting the HPD to the Raspberry Pi's GPIO line. Signed-off-by: Hans Verkuil Reviewed-by: Rob Herring --- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt index 46a0bac8b3b9..b36490aba7eb 100644 --- a/Documentation/devicetree/bindings/media/cec-gpio.txt +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt @@ -4,6 +4,10 @@ The HDMI CEC GPIO module supports CEC implementations where the CEC line is hooked up to a pull-up GPIO line and - optionally - the HPD line is hooked up to another GPIO line. +Please note: the maximum voltage for the CEC line is 3.63V, for the HPD +line it is 5.3V. So you may need some sort of level conversion circuitry +when connecting them to a GPIO line. + Required properties: - compatible: value must be "cec-gpio". - cec-gpios: gpio that the CEC line is connected to. The line should be @@ -21,7 +25,7 @@ the following property is optional: Example for the Raspberry Pi 3 where the CEC line is connected to pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is -connected to pin 11 aka BCM17: +connected to pin 11 aka BCM17 (some level shifter is needed for this!): #include