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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 897E1C43461 for ; Tue, 8 Sep 2020 18:36:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B0E42080A for ; Tue, 8 Sep 2020 18:36:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599590211; bh=XWk1HoF0lhbxsTbo9IgLLT/T2qnTbrihCczZJYn8KKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BUwhMsUNZuWSHO6Hlc8gwjnROvSPdi74Uo6QK2T5xXO+NG6l5wM1pESBm4iGwt5fC iJmK0H/sBv4rAgq6Zg048gDQpoQ+2junhB/mPPJLRJ9dHTfwuAVQbca4JF78ynGTzi 88slYN9TBs7YEEW+9lGD0emzbEpEhxzqee69D/Gw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731847AbgIHSgu (ORCPT ); Tue, 8 Sep 2020 14:36:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:53538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731346AbgIHQJE (ORCPT ); Tue, 8 Sep 2020 12:09:04 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 EE9BE2415F; Tue, 8 Sep 2020 15:49:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599580155; bh=XWk1HoF0lhbxsTbo9IgLLT/T2qnTbrihCczZJYn8KKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WXauMrpdl8TH6MQDdTZ+2qRh1JT2L0Iv1VQoNd0Y7h68Pm5sIV/UfuAVjRUVLwyAp R+CemYSxFZbmJtEz2rTvP012pJbMHsPloeQOofV/QOlHjqA/JEvzte5VS9iBfAXff4 zwg8hYzyi3X3eyAMH3edS0fBsYKzrH2WZTP71LgI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?UTF-8?q?Christian=20K=C3=B6nig?= , Kai-Heng Feng , Alex Deucher , Sasha Levin Subject: [PATCH 4.19 44/88] drm/radeon: Prefer lower feedback dividers Date: Tue, 8 Sep 2020 17:25:45 +0200 Message-Id: <20200908152223.324574445@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200908152221.082184905@linuxfoundation.org> References: <20200908152221.082184905@linuxfoundation.org> User-Agent: quilt/0.66 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 From: Kai-Heng Feng [ Upstream commit fc8c70526bd30733ea8667adb8b8ffebea30a8ed ] Commit 2e26ccb119bd ("drm/radeon: prefer lower reference dividers") fixed screen flicker for HP Compaq nx9420 but breaks other laptops like Asus X50SL. Turns out we also need to favor lower feedback dividers. Users confirmed this change fixes the regression and doesn't regress the original fix. Fixes: 2e26ccb119bd ("drm/radeon: prefer lower reference dividers") BugLink: https://bugs.launchpad.net/bugs/1791312 BugLink: https://bugs.launchpad.net/bugs/1861554 Reviewed-by: Christian König Signed-off-by: Kai-Heng Feng Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/radeon/radeon_display.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c index 3f0f3a578ddf0..c28d76d898fdb 100644 --- a/drivers/gpu/drm/radeon/radeon_display.c +++ b/drivers/gpu/drm/radeon/radeon_display.c @@ -926,7 +926,7 @@ static void avivo_get_fb_ref_div(unsigned nom, unsigned den, unsigned post_div, /* get matching reference and feedback divider */ *ref_div = min(max(den/post_div, 1u), ref_div_max); - *fb_div = DIV_ROUND_CLOSEST(nom * *ref_div * post_div, den); + *fb_div = max(nom * *ref_div * post_div / den, 1u); /* limit fb divider to its maximum */ if (*fb_div > fb_div_max) { -- 2.25.1