From patchwork Tue Sep 8 15:24:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 264192 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 712F0C43461 for ; Tue, 8 Sep 2020 19:14:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2AFCF20C09 for ; Tue, 8 Sep 2020 19:14:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599592498; bh=7j1Y0MkesorvcN29yjN4r5m84+5UT2GqpTVNZgL5Aew=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bO0vRtHteyn9ttOO3ZZsr+6MnNeOe0goUjJClERAx2UMvUgkUufx1rz7FKPi76l78 Li8jShlAAqwt8cKLfq9rKC/dkjyGniXMiEALeVW6jEeye3aWEQKpWHa/Cn8NdfEGrP Urh/MYoKqOc98mgSpLlVAlTqyeIw8IusVDS56/mA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731455AbgIHTOy (ORCPT ); Tue, 8 Sep 2020 15:14:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:52176 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731199AbgIHQEu (ORCPT ); Tue, 8 Sep 2020 12:04:50 -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 A8A9024050; Tue, 8 Sep 2020 15:38:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599579495; bh=7j1Y0MkesorvcN29yjN4r5m84+5UT2GqpTVNZgL5Aew=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dRensi2GV61U6SDBPSztMy8qMybs3tmjlmvmyZOsRH5nyUVbe1vOakQo3qmNLQXvZ U4cnd76VNv7FTBjYBolKBbQfdcbUDbCr5nUEj8uVW0usptBC39i7us88QFet3QSXib K0TbuTf+OjdbKjhTUpCbM1PC6SU3IN4fNz7fGWSA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?utf-8?q?Christian_K=C3=B6nig?= , Kai-Heng Feng , Alex Deucher , Sasha Levin Subject: [PATCH 5.8 101/186] drm/radeon: Prefer lower feedback dividers Date: Tue, 8 Sep 2020 17:24:03 +0200 Message-Id: <20200908152246.531365310@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200908152241.646390211@linuxfoundation.org> References: <20200908152241.646390211@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 df1a7eb736517..840c4bf6307fd 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) {