From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A961BC43381 for ; Mon, 25 Mar 2019 16:18:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BD5E20896 for ; Mon, 25 Mar 2019 16:18:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729414AbfCYQSU (ORCPT ); Mon, 25 Mar 2019 12:18:20 -0400 Received: from muru.com ([72.249.23.125]:42448 "EHLO muru.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725788AbfCYQSU (ORCPT ); Mon, 25 Mar 2019 12:18:20 -0400 Received: from atomide.com (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id D499C80CC; Mon, 25 Mar 2019 16:18:30 +0000 (UTC) Date: Mon, 25 Mar 2019 09:18:14 -0700 From: Tony Lindgren To: Hans Verkuil Cc: Tomi Valkeinen , Laurent Pinchart , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-omap@vger.kernel.org, Jyri Sarha Subject: Re: CEC blocks idle on omap4 Message-ID: <20190325161814.GL19425@atomide.com> References: <20190325153258.GU5717@atomide.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org * Hans Verkuil [190325 15:52]: > Hi Tony, > > On 3/25/19 4:32 PM, Tony Lindgren wrote: > > Hi Hans, > > > > Looks like CONFIG_OMAP4_DSS_HDMI_CEC=y blocks SoC core retention > > idle on omap4 if selected. > > > > Should we maybe move hdmi4_cec_init() to hdmi_display_enable() > > and hdmi4_cec_uninit() to hdmi_display_disable()? > > > > Or add some enable/disable calls in addtion to the init and > > uninit calls that can be called from hdmi_display_enable() > > and hdmi_display_disable()? > > For proper HDMI CEC behavior the CEC adapter has to remain active > even if the HPD of the display is low. Some displays pull down the > HPD when in standby, but CEC can still be used to wake them up. OK > And we see this more often as regulations for the maximum power > consumption of displays are getting more and more strict. > > So disabling CEC when the display is disabled is not an option. OK > Disabling CEC if the source is no longer transmitting isn't a good > idea either since the display will typically still send periodic > CEC commands to the source that it expects to reply to. Hmm I wonder if we could test for HPD floating and then disable cec? Then we would know nothing is connected, right? > The reality is that HDMI CEC and HDMI video are really independent of > one another. So I wonder if it isn't better to explain the downsides > of enabling CEC for the omap4 in the CONFIG_OMAP4_DSS_HDMI_CEC > description. And perhaps disable it by default? >From distro kernel point of view we should find some way to disable cec dynamically. Can we maybe do something via /sys or some command line option for cec.ko? Then if we find a way to check for floating HPD pin or something we could support that too. Regards, Tony