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 C0851C04A6A for ; Wed, 2 Aug 2023 17:25:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230201AbjHBRZZ (ORCPT ); Wed, 2 Aug 2023 13:25:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229504AbjHBRZX (ORCPT ); Wed, 2 Aug 2023 13:25:23 -0400 Received: from phobos.denx.de (phobos.denx.de [IPv6:2a01:238:438b:c500:173d:9f52:ddab:ee01]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A0B6ED for ; Wed, 2 Aug 2023 10:25:21 -0700 (PDT) Received: from [127.0.0.1] (p578adb1c.dip0.t-ipconnect.de [87.138.219.28]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: marex@denx.de) by phobos.denx.de (Postfix) with ESMTPSA id 60D5B8685D; Wed, 2 Aug 2023 19:25:18 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=denx.de; s=phobos-20191101; t=1690997119; bh=RYe5PxJYQ9XrOHJfTi636roYNO47+WQvmmqcvq5UECM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=eVFe57KoNs4YTqA0uiq3jG392qoq2aYa2ch2IpgVhL+mcKy0vY4865Ep6sV5CbRDx 0Syff0W9iVZUJjgvV3lIbIEt9E/eYpTYyDofUzVytSWx/QKmz2FKKz+utQEzPxs5Ps y5Jt2ekFNFsuevweac978G1PHlhjPxpwk+/O4UFiHhqcvrZ4TupN4OFpp6NqeGzcXw G+wWl2WfZ8nSdLAgcXTqaY+HSAonDk4G062DKQgjadTcqb6SOKSqUJI3DHtfZZTcg6 RxOsvioaIUUdVvpS5dp7/DspbZRwt4/Wc3MLMutz6IXREiKrsha86nC+1Bn1kedXvK H9gh88Mwc38Dg== Message-ID: Date: Wed, 2 Aug 2023 19:25:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.1 Subject: Re: [PATCH 2/2] drm/bridge: lt9611: Do not generate HFP/HBP/HSA and EOT packet To: neil.armstrong@linaro.org, Abhinav Kumar , Amit Pundir , Dmitry Baryshkov Cc: Jagan Teki , dri-devel@lists.freedesktop.org, Robert Foss , Andrzej Hajda , Jonas Karlman , Jernej Skrabec , Michael Walle , Laurent Pinchart , linux-arm-msm , Linux regressions mailing list , freedreno References: <20230403221233.500485-1-marex@denx.de> <20230403221233.500485-2-marex@denx.de> <4396d197-f16f-92bd-727c-eb8c78016198@quicinc.com> <961b4747-c9f1-a31c-c33c-475b4803f832@denx.de> <64c3352f-c2aa-5260-c6ff-4a607ce219a2@quicinc.com> <51d782c4-3539-c3d3-6844-d6b9a39c09eb@linaro.org> <88a49ed7-8132-3212-1f7a-9378eb640d68@denx.de> Content-Language: en-US From: Marek Vasut In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Virus-Scanned: clamav-milter 0.103.8 at phobos.denx.de X-Virus-Status: Clean Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 8/2/23 15:08, neil.armstrong@linaro.org wrote: > Hi Marek, > > On 02/08/2023 14:25, Marek Vasut wrote: >> On 8/2/23 10:39, neil.armstrong@linaro.org wrote: >>> Hi Marek, >> >> Hi, >> >>> On 13/07/2023 20:28, Marek Vasut wrote: >>> >>> >>> >>>>>> >>>>>> MIPI_DSI_MODE_VIDEO_NO_HFP means the HBP period is just skipped by >>>>>> DSIM. >>>>>> >>>>>> Maybe there is a need for new set of flags which differentiate >>>>>> between HBP skipped (i.e. NO HBP) and HBP LP11 ? >>>>>> >>>>> >>>>> No, the section of the MIPI DSI spec I posted below clearly states >>>>> there are two options: >>>>> >>>>> 1) send blanking packets during those periods >>>>> 2) transition to LP11 during those periods >>>>> >>>>> There is no 3rd option in the spec of not doing both like what you >>>>> are suggesting. So DSIM should also be only transitioning to LP11 >>>>> during those periods if its not sending the blanking packets with >>>>> those flags set. >>>>> >>>>> So, there is no need for any new set of flags to differentiate. >>>>> >>>>> The flags and their interpretation is correct in MSM driver. I >>>>> cannot comment on what exactly DSIM does with those flags. >>>> >>>> How do you explain the comment in include/drm/drm_mipi_dsi.h: >>>> >>>> 128 /* disable hback-porch area */ >>>> 129 #define MIPI_DSI_MODE_VIDEO_NO_HBP      BIT(6) >>> >>> Can you specify how you determined those flags were needed on DSIM ? >>> a vendor tree ? a datasheet ? >> >> The following upstream commit: >> >> 996e1defca344 ("drm: exynos: dsi: Fix MIPI_DSI*_NO_* mode flags") >> >>> In the meantime, we should revert this patch because it regresses >>> some Qcom >>> based platforms until we figure out what's missing to make DSIM based >>> boards >>> happy. >>> >>> I'll send a revert change afterwards. >> >> That change would break existing use case on i.MX8M then, I disagree >> with that revert. > > As I understand the timeline is : > > - 996e1defca344 was merged in v6.2-rc2 and caused regression on NXP > platforms > > - 8ddce13ae696 was merged in v6.5-rc1 to fix that but caused regression > on QCOM platforms > > Did I miss something ? That looks about right. > I don't know how to handle this apart reverting 8ddce13ae696 and trying > to find a proper fix that doesn't regress QCOM. I provided a suggestion above -- I believe QCOM is misinterpreting the NO_H* flags and it needs separate flags for its behavior. The NXP hardware per MX8M{M,N,P} reference manual (which is available at NXP.com) skips the H* areas in the transfer, which matches the flags description: include/drm/drm_mipi_dsi.h-/* disable hback-porch area */ include/drm/drm_mipi_dsi.h:#define MIPI_DSI_MODE_VIDEO_NO_HBP BIT(6) If the QCOM hardware does something else, it should introduce its own set of flags for that something else and that would be problem solved, for both platforms. I don't have access to the QCOM hardware or datasheet however, is either available ? > So, The main issue is around the real meaning of the > IPI_DSI_MODE_VIDEO_NO_* flags, > Exynos DRM removed the HSA, HBP and HFP packets, Qcom DSI moves the DSI > lanes > state to LP-11 during the period. > > The behavior is significantly different and the naming doesn't suggest any > correct behavior. > > The only solution is to find out why : > - On Qcom platforms, having the HSA, HBP and HFP periods is OK, but not > on DSIM > - On DSIM, removing the HSA, HBP and HFP periods is fine > - What's the exact requirement of the lt9611 bridge concerning those > periods See above.