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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 5273CC433ED for ; Sat, 17 Apr 2021 06:31:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21704611AB for ; Sat, 17 Apr 2021 06:31:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230269AbhDQGcJ (ORCPT ); Sat, 17 Apr 2021 02:32:09 -0400 Received: from mailoutvs2.siol.net ([185.57.226.193]:55271 "EHLO mail.siol.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229614AbhDQGcI (ORCPT ); Sat, 17 Apr 2021 02:32:08 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.siol.net (Zimbra) with ESMTP id BF64B523653; Sat, 17 Apr 2021 08:31:40 +0200 (CEST) X-Virus-Scanned: amavisd-new at psrvmta12.zcs-production.pri Received: from mail.siol.net ([127.0.0.1]) by localhost (psrvmta12.zcs-production.pri [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id n-saAgAigrm7; Sat, 17 Apr 2021 08:31:40 +0200 (CEST) Received: from mail.siol.net (localhost [127.0.0.1]) by mail.siol.net (Zimbra) with ESMTPS id 749A95238C1; Sat, 17 Apr 2021 08:31:40 +0200 (CEST) Received: from jernej-laptop.localnet (89-212-178-211.dynamic.t-2.net [89.212.178.211]) (Authenticated sender: jernej.skrabec@siol.net) by mail.siol.net (Zimbra) with ESMTPA id E0502523653; Sat, 17 Apr 2021 08:31:39 +0200 (CEST) From: Jernej =?utf-8?B?xaBrcmFiZWM=?= To: Laurent Pinchart , Neil Armstrong Cc: jonas@kwiboo.se, robert.foss@linaro.org, dri-devel@lists.freedesktop.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hverkuil-cisco@xs4all.nl Subject: Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver Date: Sat, 17 Apr 2021 08:31:39 +0200 Message-ID: <9525152.Q8VVBrNj5Z@jernej-laptop> In-Reply-To: <96b9e144-0791-4c19-3e3c-b0e9efb86138@baylibre.com> References: <20210416092737.1971876-1-narmstrong@baylibre.com> <96b9e144-0791-4c19-3e3c-b0e9efb86138@baylibre.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org CC Hans Verkuil Dne petek, 16. april 2021 ob 13:38:59 CEST je Neil Armstrong napisal(a): > On 16/04/2021 11:58, Laurent Pinchart wrote: > > Hi Neil, > > > > On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote: > >> This adds DW-HDMI driver a glue option to disable loading of the CEC > >> sub-driver. > >> > >> On some SoCs, the CEC functionality is enabled in the IP config bits, but > >> the CEC bus is non-functional like on Amlogic SoCs, where the CEC config > >> bit is set but the DW-HDMI CEC signal is not connected to a physical > >> pin, leading to some confusion when the DW-HDMI CEC controller can't > >> communicate on the bus.> > > If we can't trust the CEC config bit, would it be better to not use it > > at all, and instead let each platform glue logic tell whether to enable > > CEC or not ? > > Actually, the CEC config bit is right, the HW exists and should be > functional, but this bit doesn't tell if the CEC signal is connected to > something. I'm in favour of Neil's solution. Currently we have only one exception. > > This lies in the IP integration, like other bits under the > "amlogic,meson-*-dw-hdmi" umbrella. > > The first attempt was by Hans using DT, but adding a property in DT for a > vendor specific compatible doesn't make sense. Another idea would be to > describe the CEC signal endpoint like we do for video signal, but I think > this is out of scope and this solution is much simpler and straightforward, > and it's more an exception than a general use case to solve. Note that we still need DT property for disabling CEC. I have one Allwinner H3 board where board designer decided to use GPIO CEC implementation instead of DW HDMI one (vendor Linux doesn't implement DW HDMI CEC driver). Other H3 boards happily use DW HDMI CEC. Best regards, Jernej > > Neil > > >> Jernej Skrabec (1): > >> drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC > >> > >> driver > >> > >> Neil Armstrong (1): > >> drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver > >> > >> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +- > >> drivers/gpu/drm/meson/meson_dw_hdmi.c | 1 + > >> include/drm/bridge/dw_hdmi.h | 2 ++ > >> 3 files changed, 4 insertions(+), 1 deletion(-)