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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5578FC433F5 for ; Wed, 19 Jan 2022 06:42:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345299AbiASGmA (ORCPT ); Wed, 19 Jan 2022 01:42:00 -0500 Received: from mo4-p02-ob.smtp.rzone.de ([85.215.255.84]:39903 "EHLO mo4-p02-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344439AbiASGle (ORCPT ); Wed, 19 Jan 2022 01:41:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1642574425; s=strato-dkim-0002; d=goldelico.com; h=To:References:Message-Id:Cc:Date:In-Reply-To:From:Subject:Cc:Date: From:Subject:Sender; bh=soxn4qgkDsTZ0oHmNOMh5qyy1VH0WMra/yBF1KFdkyA=; b=mDhwJ6A64h1u9LKK91u8VrQk1niBls3lKkpkpSbsdonYHAbR2zvclGS4ElY+YlQE6X fdxktMrEev2PpoaFbcDAfvKyz7p/5WGRLIPykNQlp4JGybb+DUwJrriEcRTJmp6rl0iK AGTQicUwQEAN2gzfGzeIIYDtRgbl3RY/Z0NlxJ8jngZ+nRiTUT+S/9RpF7R8n9Q+/FYe cqioEpmJzUVviuwTRMzFBG5LqoYZfrUHD1IKM0suKDpyDI3Nq8yk77dLqKzs2jlm26Zp 8ZeT/QrooqXvw2LpQGw9H+bl14ilb2yJq2uyv/UH3F8VUsBEsIioNgbTJhQ7NS1HPHpZ zUDg== Authentication-Results: strato.com; dkim=none X-RZG-AUTH: ":JGIXVUS7cutRB/49FwqZ7WcJeFKiMgPgp8VKxflSZ1P34KBj4Qpw9iZeHWElw4TlkQ==" X-RZG-CLASS-ID: mo00 Received: from imac.fritz.box by smtp.strato.de (RZmta 47.37.6 DYNA|AUTH) with ESMTPSA id D61423y0J6eNjFW (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (curve X9_62_prime256v1 with 256 ECDH bits, eq. 3072 bits RSA)) (Client did not present a certificate); Wed, 19 Jan 2022 07:40:23 +0100 (CET) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.21\)) Subject: Re: [PATCH v5 2/7] drm/ingenic: Add support for JZ4780 and HDMI output From: "H. Nikolaus Schaller" In-Reply-To: <13356060.GkHXLIg068@jason> Date: Wed, 19 Jan 2022 07:40:22 +0100 Cc: Paul Cercueil , Mark Rutland , Geert Uytterhoeven , Neil Armstrong , David Airlie , dri-devel , linux-mips , Andrzej Hajda , Laurent Pinchart , Miquel Raynal , Sam Ravnborg , Jernej Skrabec , Harry Wentland , OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS , Kees Cook , Jonas Karlman , Mark Brown , Maxime Ripard , Thomas Bogendoerfer , Liam Girdwood , Robert Foss , linux-kernel , Rob Herring , Daniel Vetter , Hans Verkuil , Discussions about the Letux Kernel Content-Transfer-Encoding: quoted-printable Message-Id: References: <13356060.GkHXLIg068@jason> To: Paul Boddie X-Mailer: Apple Mail (2.3445.104.21) Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Hi Paul, > Am 18.01.2022 um 23:59 schrieb Paul Boddie : >=20 > On Tuesday, 18 January 2022 17:58:58 CET Paul Cercueil wrote: >>=20 >> Not at all. If the clock is disabled, the LCD controller is disabled, >> so all the registers read zero, this makes sense. You can only read = the >> registers when the clock is enabled. On some SoCs, reading disabled >> registers can even cause a complete lockup. >=20 > My concern was that something might be accessing the registers before = the=20 > clock had been enabled. It seems unlikely, given that the clock is = enabled in=20 > the bind function, and I would have thought that nothing would invoke = the=20 > different driver operations ("funcs") until bind has been called, nor = should=20 > anything called from within bind itself be accessing registers. >=20 >> Why is this JZ_LCD_OSDC_ALPHAEN bit needed now? I remember it working >> fine last time I tried, and now I indeed get a black screen unless = this >> bit is set. The PM doesn't make it obvious that the bit is required, >> but that wouldn't be surprising. >=20 > It isn't actually needed. If the DMA descriptors are set up = appropriately, the=20 > OSD alpha bit seems to be set as a consequence. In my non-Linux = testing=20 > environment I don't even set any OSD registers explicitly, but the OSD = alpha=20 > and enable flags become set when the display is active. Is it set by DMA descriptors or by explicit code? We did have an explicit setting of JZ_LCD_OSDC_ALPHAEN https://www.spinics.net/lists/devicetree/msg438447.html but that was postponed for further discussion. And now if we add it (from basic functionality) back, it is fine again. BR, Nikolaus=