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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86BE3C10F04 for ; Fri, 1 Dec 2023 09:04:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377952AbjLAJEg (ORCPT ); Fri, 1 Dec 2023 04:04:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377855AbjLAJEd (ORCPT ); Fri, 1 Dec 2023 04:04:33 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A8F2128 for ; Fri, 1 Dec 2023 01:04:40 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79AB7C433C7; Fri, 1 Dec 2023 09:04:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701421479; bh=atyrbWt1APFwyakv3t85xJ2Im36Fb7nRp4IPSv5aSwI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=d2/GeTv5fmEHAm0HeO/YrJA1NnZg9OhpV5zCEMH+MHmVcDU6/Ef1MbZTT4rY1SqoV PH1Hk/oTngCJ4CyyMr0B/NdOU5A20BzceTolDt+CUrAQLpFjikE++aMXjnM/U5kMeR T5LRPEjX4u5EqcVOLq+x69c46Slxx72iplptDgL9f9+DstJn3+Mwe1Qpu6gIiQpabj Jf1nB526Rso2bqW+f6WuFCAB3CNt8SJBtauBpKWwIL5tQdg5IokVf7KeijskhJomxt gdREw3LJkAF6rmQwe2VlQtRna/bDC2y0n4Ph2/BbTM99iRatOycPHyl12Zof0TwtCy /8ZJ/oU+/LsSw== MIME-Version: 1.0 Date: Fri, 01 Dec 2023 10:04:33 +0100 From: Michael Walle To: Inki Dae , Jagan Teki , Marek Szyprowski , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , David Airlie , Daniel Vetter , Frieder Schrempf , Tim Harvey , Alexander Stein Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm: bridge: samsung-dsim: Don't use FORCE_STOP_STATE In-Reply-To: <20231113164344.1612602-1-mwalle@kernel.org> References: <20231113164344.1612602-1-mwalle@kernel.org> Message-ID: <631fe35a2a3b00781231e4f3f5094fae@kernel.org> X-Sender: mwalle@kernel.org Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > The FORCE_STOP_STATE bit is unsuitable to force the DSI link into LP-11 > mode. It seems the bridge internally queues DSI packets and when the > FORCE_STOP_STATE bit is cleared, they are sent in close succession > without any useful timing (this also means that the DSI lanes won't go > into LP-11 mode). The length of this gibberish varies between 1ms and > 5ms. This sometimes breaks an attached bridge (TI SN65DSI84 in this > case). In our case, the bridge will fail in about 1 per 500 reboots. > > The FORCE_STOP_STATE handling was introduced to have the DSI lanes in > LP-11 state during the .pre_enable phase. But as it turns out, none of > this is needed at all. Between samsung_dsim_init() and > samsung_dsim_set_display_enable() the lanes are already in LP-11 mode. > The code as it was before commit 20c827683de0 ("drm: bridge: > samsung-dsim: Fix init during host transfer") and 0c14d3130654 ("drm: > bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") was correct > in this regard. > > This patch basically reverts both commits. It was tested on an i.MX8M > SoC with an SN65DSI84 bridge. The signals were probed and the DSI > packets were decoded during initialization and link start-up. After > this > patch the first DSI packet on the link is a VSYNC packet and the timing > is correct. > > Command mode between .pre_enable and .enable was also briefly tested by > a quick hack. There was no DSI link partner which would have responded, > but it was made sure the DSI packet was send on the link. As a side > note, the command mode seems to just work in HS mode. I couldn't find > that the bridge will handle commands in LP mode. > > Fixes: 20c827683de0 ("drm: bridge: samsung-dsim: Fix init during host > transfer") > Fixes: 0c14d3130654 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow > to meet spec") > Signed-off-by: Michael Walle > --- > Let me know wether this should be two commits each reverting one, but > both > commits appeared first in kernel 6.5. Are there any news? -michael