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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C900DCA0EC0 for ; Mon, 11 Aug 2025 08:26:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=2DRTDdeB+RuKBnxoHGmxhWMtMDlk8vl0RydIHruRq9A=; b=kK4+IaiXF+fJYRWAsXmXuva5zU DtOb/8kdSBXEbA2ShQtlI7sPqnji6N0Wi6tobI8P6u4LG0zCpSXe+/zBYt3RBCvn5thlsPiNjDrJq 9u/kyFWqWLyvUtMJ0dM/HvxBdAJHQndOvOYRomGLIgaQb1Uepw6SxJQgIwF8eZvdm2Pv7tGuOVMKS bFj9ma1sk1FqRhixkWtsCGAMKq9iGX2eL3uAp9M3rkxIW3PSoTTXx3BXQifn7J+gtjKHBiGEtTXIn Kt92Z6R/OtQfNshhLLxb69xN5SYmBnHvHygHH/KdgmNrU6OivGdhCTEiAhT8EOz+ZdFoducoxBKim W0Kgo+4A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulNrj-00000006qjf-38c8; Mon, 11 Aug 2025 08:26:47 +0000 Received: from perceval.ideasonboard.com ([213.167.242.64]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1ulNOO-00000006m1N-1Zp5 for linux-arm-kernel@lists.infradead.org; Mon, 11 Aug 2025 07:56:29 +0000 Received: from [192.168.88.20] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 7A2C3379; Mon, 11 Aug 2025 09:55:30 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1754898931; bh=Us9A02rAfeWiFHHEg4K6xC2IqA5Evy6GkingApnfNlM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=rFoAuifd0sJhbR96hiXqxC/n9dntL5Twzb1c9AbhkNgzA11a36PGDQPkBQnwklBR7 ugKaBk2ryyWFHMrbpCFm0lRyRi0QE3s3mOe8uVsZlAxof1FY//UiCRawdocpMmbNF7 pGmgHqhjuQieQfhBl7wbu81ThEsXDX2qjMIFWke4= Message-ID: Date: Mon, 11 Aug 2025 10:56:19 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] drm/tidss: Fixes data edge sampling To: devarsh , Louis Chauvet Cc: thomas.petazzoni@bootlin.com, Jyri Sarha , Tomi Valkeinen , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org, Jyri Sarha , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Sam Ravnborg , Benoit Parrot , Lee Jones , Nishanth Menon , Vignesh Raghavendra , Tero Kristo , s-jain1@ti.com References: <20250730-fix-edge-handling-v1-0-1bdfb3fe7922@bootlin.com> <1951ecfe-d080-464c-8441-f5400f535495@ideasonboard.com> <19dd9aa9-43c6-4483-9cdf-f297e41ecdec@ti.com> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; keydata= xsFNBE6ms0cBEACyizowecZqXfMZtnBniOieTuFdErHAUyxVgtmr0f5ZfIi9Z4l+uUN4Zdw2 wCEZjx3o0Z34diXBaMRJ3rAk9yB90UJAnLtb8A97Oq64DskLF81GCYB2P1i0qrG7UjpASgCA Ru0lVvxsWyIwSfoYoLrazbT1wkWRs8YBkkXQFfL7Mn3ZMoGPcpfwYH9O7bV1NslbmyJzRCMO eYV258gjCcwYlrkyIratlHCek4GrwV8Z9NQcjD5iLzrONjfafrWPwj6yn2RlL0mQEwt1lOvn LnI7QRtB3zxA3yB+FLsT1hx0va6xCHpX3QO2gBsyHCyVafFMrg3c/7IIWkDLngJxFgz6DLiA G4ld1QK/jsYqfP2GIMH1mFdjY+iagG4DqOsjip479HCWAptpNxSOCL6z3qxCU8MCz8iNOtZk DYXQWVscM5qgYSn+fmMM2qN+eoWlnCGVURZZLDjg387S2E1jT/dNTOsM/IqQj+ZROUZuRcF7 0RTtuU5q1HnbRNwy+23xeoSGuwmLQ2UsUk7Q5CnrjYfiPo3wHze8avK95JBoSd+WIRmV3uoO rXCoYOIRlDhg9XJTrbnQ3Ot5zOa0Y9c4IpyAlut6mDtxtKXr4+8OzjSVFww7tIwadTK3wDQv Bus4jxHjS6dz1g2ypT65qnHen6mUUH63lhzewqO9peAHJ0SLrQARAQABzTBUb21pIFZhbGtl aW5lbiA8dG9taS52YWxrZWluZW5AaWRlYXNvbmJvYXJkLmNvbT7CwY4EEwEIADgWIQTEOAw+ ll79gQef86f6PaqMvJYe9QUCX/HruAIbAwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgAAKCRD6 PaqMvJYe9WmFD/99NGoD5lBJhlFDHMZvO+Op8vCwnIRZdTsyrtGl72rVh9xRfcSgYPZUvBuT VDxE53mY9HaZyu1eGMccYRBaTLJSfCXl/g317CrMNdY0k40b9YeIX10feiRYEWoDIPQ3tMmA 0nHDygzcnuPiPT68JYZ6tUOvAt7r6OX/litM+m2/E9mtp8xCoWOo/kYO4mOAIoMNvLB8vufi uBB4e/AvAjtny4ScuNV5c5q8MkfNIiOyag9QCiQ/JfoAqzXRjVb4VZG72AKaElwipiKCWEcU R4+Bu5Qbaxj7Cd36M/bI54OrbWWETJkVVSV1i0tghCd6HHyquTdFl7wYcz6cL1hn/6byVnD+ sR3BLvSBHYp8WSwv0TCuf6tLiNgHAO1hWiQ1pOoXyMEsxZlgPXT+wb4dbNVunckwqFjGxRbl Rz7apFT/ZRwbazEzEzNyrBOfB55xdipG/2+SmFn0oMFqFOBEszXLQVslh64lI0CMJm2OYYe3 PxHqYaztyeXsx13Bfnq9+bUynAQ4uW1P5DJ3OIRZWKmbQd/Me3Fq6TU57LsvwRgE0Le9PFQs dcP2071rMTpqTUteEgODJS4VDf4lXJfY91u32BJkiqM7/62Cqatcz5UWWHq5xeF03MIUTqdE qHWk3RJEoWHWQRzQfcx6Fn2fDAUKhAddvoopfcjAHfpAWJ+ENc7BTQROprNHARAAx0aat8GU hsusCLc4MIxOQwidecCTRc9Dz/7U2goUwhw2O5j9TPqLtp57VITmHILnvZf6q3QAho2QMQyE DDvHubrdtEoqaaSKxKkFie1uhWNNvXPhwkKLYieyL9m2JdU+b88HaDnpzdyTTR4uH7wk0bBa KbTSgIFDDe5lXInypewPO30TmYNkFSexnnM3n1PBCqiJXsJahE4ZQ+WnV5FbPUj8T2zXS2xk 0LZ0+DwKmZ0ZDovvdEWRWrz3UzJ8DLHb7blPpGhmqj3ANXQXC7mb9qJ6J/VSl61GbxIO2Dwb xPNkHk8fwnxlUBCOyBti/uD2uSTgKHNdabhVm2dgFNVuS1y3bBHbI/qjC3J7rWE0WiaHWEqy UVPk8rsph4rqITsj2RiY70vEW0SKePrChvET7D8P1UPqmveBNNtSS7In+DdZ5kUqLV7rJnM9 /4cwy+uZUt8cuCZlcA5u8IsBCNJudxEqBG10GHg1B6h1RZIz9Q9XfiBdaqa5+CjyFs8ua01c 9HmyfkuhXG2OLjfQuK+Ygd56mV3lq0aFdwbaX16DG22c6flkkBSjyWXYepFtHz9KsBS0DaZb 4IkLmZwEXpZcIOQjQ71fqlpiXkXSIaQ6YMEs8WjBbpP81h7QxWIfWtp+VnwNGc6nq5IQDESH mvQcsFS7d3eGVI6eyjCFdcAO8eMAEQEAAcLBXwQYAQIACQUCTqazRwIbDAAKCRD6PaqMvJYe 9fA7EACS6exUedsBKmt4pT7nqXBcRsqm6YzT6DeCM8PWMTeaVGHiR4TnNFiT3otD5UpYQI7S suYxoTdHrrrBzdlKe5rUWpzoZkVK6p0s9OIvGzLT0lrb0HC9iNDWT3JgpYDnk4Z2mFi6tTbq xKMtpVFRA6FjviGDRsfkfoURZI51nf2RSAk/A8BEDDZ7lgJHskYoklSpwyrXhkp9FHGMaYII m9EKuUTX9JPDG2FTthCBrdsgWYPdJQvM+zscq09vFMQ9Fykbx5N8z/oFEUy3ACyPqW2oyfvU CH5WDpWBG0s5BALp1gBJPytIAd/pY/5ZdNoi0Cx3+Z7jaBFEyYJdWy1hGddpkgnMjyOfLI7B CFrdecTZbR5upjNSDvQ7RG85SnpYJTIin+SAUazAeA2nS6gTZzumgtdw8XmVXZwdBfF+ICof 92UkbYcYNbzWO/GHgsNT1WnM4sa9lwCSWH8Fw1o/3bX1VVPEsnESOfxkNdu+gAF5S6+I6n3a ueeIlwJl5CpT5l8RpoZXEOVtXYn8zzOJ7oGZYINRV9Pf8qKGLf3Dft7zKBP832I3PQjeok7F yjt+9S+KgSFSHP3Pa4E7lsSdWhSlHYNdG/czhoUkSCN09C0rEK93wxACx3vtxPLjXu6RptBw 3dRq7n+mQChEB1am0BueV1JZaBboIL0AGlSJkm23kw== In-Reply-To: <19dd9aa9-43c6-4483-9cdf-f297e41ecdec@ti.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250811_005628_550874_9AA1D328 X-CRM114-Status: GOOD ( 20.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 08/08/2025 16:24, devarsh wrote: > Hi Tomi, Louis, > > On 07/08/25 18:51, Tomi Valkeinen wrote: >> Hi, >> >> On 30/07/2025 20:02, Louis Chauvet wrote: >>> Currently the driver only configure the data edge sampling partially. The >>> AM62 require it to be configured in two distincts registers: one in tidss >>> and one in the general device registers. >>> >>> Introduce a new dt property to link the proper syscon node from the main >>> device registers into the tidss driver. >>> >>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem") >>> --- >>> Cc: stable@vger.kernel.org >>> >>> Signed-off-by: Louis Chauvet >> >> I understand why you call this a fix, but I think this is not really a >> fix. From looking at the patches, my understanding is that for DPI >> outputs we have always only supported certain clock/data edge. > > I don't think driver makes a distinction between supported/unsupported > or errors out in case it is run with "different" clock/data edge panel > (for e.g DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE is set per the panel > configuration). Instead it tries to program the VP registers per the > DRM_BUS_FLAG* getting passed by framework per the connected panel and > gives an incorrect behavior if those are different than defaults since > those settings are not sufficient for these displays and instead extra > MMR register settings are also required. Well, this gets into the meaning of "fix". I didn't right away see an explicit definition in the kernel docs. When the tidss driver was added, neither AM62x nor AM62A existed. Yet this series "fixes" the original tidss commit for AM62x and AM62A? And the patch proposes that this series is to be backported to stable kernels going back to the original tidss commit? When AM62x and AM62A support was added to the tidss, this feature was not in the driver. So this is clearly also not a regression. Missing this feature causes no crashes or other system level misbehavior. It only causes the panels (that have never been supported with tidss on AM62x and AM62A) to show garbage. So we have a driver, to which support for new SoCs was added at some later point, and at that point we did not add support for all kinds of panels. Is adding support for those panels a new feature or a bug fix? Should it be backported to stable kernels? Documentation/process/stable-kernel-rules.rst has some guidelines. Maybe one could argue that this is a "hardware quirk" mentioned there, or perhaps "add a device ID" (of sorts). I might agree, if this was an easily backportable, totally non-controversial, one-liner style patch with no chance of regressions. Maybe the next version will be, but this one is not. Tomi