From nobody Fri Dec 19 20:52:33 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 036A6C32774 for ; Tue, 23 Aug 2022 09:40:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351727AbiHWJkJ (ORCPT ); Tue, 23 Aug 2022 05:40:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241877AbiHWJjP (ORCPT ); Tue, 23 Aug 2022 05:39:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D52B77EA0; Tue, 23 Aug 2022 01:41:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EDC2A6153A; Tue, 23 Aug 2022 08:41:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBFEAC433C1; Tue, 23 Aug 2022 08:41:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661244065; bh=xhRxOo1GPiaDygVWyNltCZqUz115iKckMGsylEzVE1k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TeanYzm+rEjGQrXKX/nLzp6WEH7Ev5FS+385acPwZ72XQ7PMki49Hxsw+6In1Agpc eBGTURkcolhCwumohw8twWVOxe2d9Ja52WVyUMcjshm0l0EtY1Ieo0bmNY3lCVXnmQ 0QYUY9X2y8C5LhxM7/jnay5f6qKIkDfCBDJblfRo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Stevenson , Maxime Ripard , Sasha Levin Subject: [PATCH 4.14 067/229] drm/vc4: dsi: Correct DSI divider calculations Date: Tue, 23 Aug 2022 10:23:48 +0200 Message-Id: <20220823080056.115431219@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080053.202747790@linuxfoundation.org> References: <20220823080053.202747790@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Dave Stevenson [ Upstream commit 3b45eee87da171caa28f61240ddb5c21170cda53 ] The divider calculations tried to find the divider just faster than the clock requested. However if it required a divider of 7 then the for loop aborted without handling the "error" case, and could end up with a clock lower than requested. The integer divider from parent PLL to DSI clock is also capable of going up to /255, not just /7 that the driver was trying. This allows for slower link frequencies on the DSI bus where the resolution permits. Correct the loop so that we always have a clock greater than requested, and covering the whole range of dividers. Fixes: 86c1b9eff3f2 ("drm/vc4: Adjust modes in DSI to work around the integ= er PLL divider.") Signed-off-by: Dave Stevenson Link: https://lore.kernel.org/r/20220613144800.326124-13-maxime@cerno.tech Signed-off-by: Maxime Ripard Signed-off-by: Sasha Levin --- drivers/gpu/drm/vc4/vc4_dsi.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index 04796d7d0fdb..33d27f4acec0 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -846,11 +846,9 @@ static bool vc4_dsi_encoder_mode_fixup(struct drm_enco= der *encoder, /* Find what divider gets us a faster clock than the requested * pixel clock. */ - for (divider =3D 1; divider < 8; divider++) { - if (parent_rate / divider < pll_clock) { - divider--; + for (divider =3D 1; divider < 255; divider++) { + if (parent_rate / (divider + 1) < pll_clock) break; - } } =20 /* Now that we've picked a PLL divider, calculate back to its --=20 2.35.1