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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT 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 90B90C2F3A0 for ; Mon, 21 Jan 2019 14:02:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C76420989 for ; Mon, 21 Jan 2019 14:02:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548079367; bh=s85YtZrR2NcAWvIX7Mzr15oHV+WicK1iRPGXMn9GlHA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DDcC/awN0Lwgmg/YROzdmyxTaTYm6V/2CEecblwpjhCsEYjdaxTYNbnqDPqMQPSBa otd0l0FJHYY4tCOMSaK18IcWNA684oYBLg9igu75NFKz2kvRxH0ypuyoJwdozz1/7J ZuJL/Rm5uXeyH/gxX+38CFfL4gfuWY1gy8tXLsTg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732870AbfAUOCp (ORCPT ); Mon, 21 Jan 2019 09:02:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:50446 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731464AbfAUOCn (ORCPT ); Mon, 21 Jan 2019 09:02:43 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B5F8020989; Mon, 21 Jan 2019 14:02:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548079362; bh=s85YtZrR2NcAWvIX7Mzr15oHV+WicK1iRPGXMn9GlHA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fF74a+DZDEo41J6LzCcTU1yP6XpFDhEPF7m51TGTE6B6qk38z5dmpUwV5Z5bOaiQW NTac+sbjSZff1v2iAbHhlKwzxooqYQe+swS0R/LVyeruwFFD2Eaepa7+URi3l6OmR1 gfb/kKifGRFM+PsdDATDRjkI7Jyi5kkm0SVChVjo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ivan Mironov , Daniel Vetter Subject: [PATCH 4.19 98/99] drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock Date: Mon, 21 Jan 2019 14:49:30 +0100 Message-Id: <20190121134919.998208187@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190121134913.924726465@linuxfoundation.org> References: <20190121134913.924726465@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ivan Mironov commit 66a8d5bfb518f9f12d47e1d2dce1732279f9451e upstream. Strict requirement of pixclock to be zero breaks support of SDL 1.2 which contains hardcoded table of supported video modes with non-zero pixclock values[1]. To better understand which pixclock values are considered valid and how driver should handle these values, I briefly examined few existing fbdev drivers and documentation in Documentation/fb/. And it looks like there are no strict rules on that and actual behaviour varies: * some drivers treat (pixclock == 0) as "use defaults" (uvesafb.c); * some treat (pixclock == 0) as invalid value which leads to -EINVAL (clps711x-fb.c); * some pass converted pixclock value to hardware (uvesafb.c); * some are trying to find nearest value from predefined table (vga16fb.c, video_gx.c). Given this, I believe that it should be safe to just ignore this value if changing is not supported. It seems that any portable fbdev application which was not written only for one specific device working under one specific kernel version should not rely on any particular behaviour of pixclock anyway. However, while enabling SDL1 applications to work out of the box when there is no /etc/fb.modes with valid settings, this change affects the video mode choosing logic in SDL. Depending on current screen resolution, contents of /etc/fb.modes and resolution requested by application, this may lead to user-visible difference (not always): image will be displayed in a right way, but it will be aligned to the left instead of center. There is no "right behaviour" here as well, as emulated fbdev, opposing to old fbdev drivers, simply ignores any requsts of video mode changes with resolutions smaller than current. The easiest way to reproduce this problem is to install sdl-sopwith[2], remove /etc/fb.modes file if it exists, and then try to run sopwith from console without X. At least in Fedora 29, sopwith may be simply installed from standard repositories. [1] SDL 1.2.15 source code, src/video/fbcon/SDL_fbvideo.c, vesa_timings [2] http://sdl-sopwith.sourceforge.net/ Signed-off-by: Ivan Mironov Cc: stable@vger.kernel.org Fixes: 79e539453b34e ("DRM: i915: add mode setting support") Fixes: 771fe6b912fca ("drm/radeon: introduce kernel modesetting for radeon hardware") Fixes: 785b93ef8c309 ("drm/kms: move driver specific fb common code to helper functions (v2)") Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20190108072353.28078-3-mironov.ivan@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_fb_helper.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1690,9 +1690,14 @@ int drm_fb_helper_check_var(struct fb_va struct drm_fb_helper *fb_helper = info->par; struct drm_framebuffer *fb = fb_helper->fb; - if (var->pixclock != 0 || in_dbg_master()) + if (in_dbg_master()) return -EINVAL; + if (var->pixclock != 0) { + DRM_DEBUG("fbdev emulation doesn't support changing the pixel clock, value of pixclock is ignored\n"); + var->pixclock = 0; + } + /* * Changes struct fb_var_screeninfo are currently not pushed back * to KMS, hence fail if different settings are requested.