From patchwork Tue Aug 25 17:33:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kai-Heng Feng X-Patchwork-Id: 11737585 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BDCBC1731 for ; Wed, 26 Aug 2020 08:05:59 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A404220866 for ; Wed, 26 Aug 2020 08:05:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A404220866 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=canonical.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2D52689CDB; Wed, 26 Aug 2020 08:05:53 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3B2916E948; Tue, 25 Aug 2020 17:34:02 +0000 (UTC) Received: from 61-220-137-37.hinet-ip.hinet.net ([61.220.137.37] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1kAcpa-0003xk-Fg; Tue, 25 Aug 2020 17:33:59 +0000 From: Kai-Heng Feng To: alexander.deucher@amd.com, christian.koenig@amd.com Subject: [PATCH] drm/radeon: Prefer lower feedback dividers Date: Wed, 26 Aug 2020 01:33:48 +0800 Message-Id: <20200825173349.24580-1-kai.heng.feng@canonical.com> X-Mailer: git-send-email 2.17.1 X-Mailman-Approved-At: Wed, 26 Aug 2020 08:04:49 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , open list , "open list:DRM DRIVERS" , Kai-Heng Feng , "open list:RADEON and AMDGPU DRM DRIVERS" MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 Signed-off-by: Kai-Heng Feng Reviewed-by: Christian König --- 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 e0ae911ef427..7b69d6dfe44a 100644 --- a/drivers/gpu/drm/radeon/radeon_display.c +++ b/drivers/gpu/drm/radeon/radeon_display.c @@ -933,7 +933,7 @@ 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) {