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,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 AB948C433FE for ; Sun, 13 Dec 2020 13:21:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A02D22EBE for ; Sun, 13 Dec 2020 13:21:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406772AbgLMNVE (ORCPT ); Sun, 13 Dec 2020 08:21:04 -0500 Received: from ste-pvt-msa1.bahnhof.se ([213.80.101.70]:3231 "EHLO ste-pvt-msa1.bahnhof.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406755AbgLMNU5 (ORCPT ); Sun, 13 Dec 2020 08:20:57 -0500 Received: from localhost (localhost [127.0.0.1]) by ste-pvt-msa1.bahnhof.se (Postfix) with ESMTP id 9BB723F99B; Sun, 13 Dec 2020 14:20:11 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from ste-pvt-msa1.bahnhof.se ([127.0.0.1]) by localhost (ste-pvt-msa1.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Yz9lJqpYhZ98; Sun, 13 Dec 2020 14:20:10 +0100 (CET) Received: by ste-pvt-msa1.bahnhof.se (Postfix) with ESMTPA id 87A783F859; Sun, 13 Dec 2020 14:20:10 +0100 (CET) Date: Sun, 13 Dec 2020 14:20:10 +0100 From: Fredrik Noring To: Jiaxun Yang Cc: linux-mips@vger.kernel.org, Aaro Koskinen , "Maciej W. Rozycki" Subject: Re: [PATCH 094/120] MIPS: PS2: FB: Frame buffer driver for the PlayStation 2 Message-ID: References: <4927c42fb3401c42c4c5a077f272331ac79d80b1.1567326213.git.noring@nocrew.org> <1003c9cc-c30e-00a7-7494-4f1cb4862e88@flygoat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1003c9cc-c30e-00a7-7494-4f1cb4862e88@flygoat.com> Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Mon, Sep 02, 2019 at 09:12:22AM +0800, Jiaxun Yang wrote: > According to kernel policy[1] no more new FBDev driver would be accepted. > > Please refactor it to DRM. I obtained a functional DRM driver a while back, but unfortunately it's a poor fit on the hardware, for the following reasons, in brief: The DRM subsystem (in general) breaks user-space in significant ways: - fbset command timing mode settings are ignored; - attempts to set modes with /sys/class/graphics/fb0/mode are ignored; - /sys/class/graphics/fb0/modes outputs incorrect refresh rates; - relevant modes are missing in /sys/class/graphics/fb0/modes; - the standard DRM video modes seem to mix up the sync and front porch timings in struct drm_display_mode but this remains to be confirmed. DRM seems to rely heavily on EDID to negotiate a video resolution, but EDID isn't available with vintage analogue display hardware. The Graphics Synthesizer (GS) hardware is essentially a serial device that accepts sequences of commands with data via DMA. Notably, it cannot be memory mapped. Can the GS be modelled, in a reasonable way, on existing kernel video interfaces, when taking memory efficiency and performance into account? For anyone who is interested: In addition to this patch series and its documentation references, some background information and details on the Graphics Synthesizer are available here: https://github.com/frno7/linux/issues/10 Fredrik