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 99591C0218A for ; Thu, 30 Jan 2025 15:20:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yTncfTDyLX0GGreyqE4yUOgQj5uXC1+fBgd56hD5oaM=; b=LYm16p2wGDQ2a6 RxyyDoVQOEIQypmYw+R+sNeWWiQqlCyPsx5p/SoTJtbpBZLON2IxPmHALVnj75UcWI2i/XruZA2Af ylLlCdyrfXwxLLTPo8S8mycWaj+eaX1DwOndoBZBQE5yvpPihHwxbydbOQhjxWD1MkEq6oYXF5T1/ eFLq6lRDR17l+ES0NddIS9ZgUI6e0vSeeUYDdIm+n4ee9np01LyQ1/3W8XiZu2fC7n64lKhu6msny pdZezW/OR72zvCprOk1OU5N4e3mEWsylU9v3PNshB+eGi4wqxTe+4Y0GXgF+kXPUY/pP7h/vALJw9 Mi/by2cF9Bk/sbbpYmeg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tdWKp-000000093VS-47Gn; Thu, 30 Jan 2025 15:20:03 +0000 Received: from relay6-d.mail.gandi.net ([217.70.183.198]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tdWKl-000000093Ue-3f4o for linux-mtd@lists.infradead.org; Thu, 30 Jan 2025 15:20:01 +0000 Received: by mail.gandi.net (Postfix) with ESMTPSA id 535D544280; Thu, 30 Jan 2025 15:19:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1738250395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mthSOymJzZU3NBmJRQSU6dHuOu/XGt2aFg8/OQCwRBI=; b=hlX/R9OCvuRRz9TzdoX5x2NhDsPTeQ5LsAlA0ZE7l7BchG9XBhMUjmgWYMOP8J0Ifhwxh7 8Th0Hg2aH6+/RaAmzvGY6hY/vWhXV2lPSwbf5kEdzEO4gK4zbdywX+RwxhILhoRKy7jQM6 fNkqlkYEMNYV78vY1/vJ5p2iThdAi4sITHhKRjz/Zw7kZSDEIU9auSE+P43fmxl/pWTpKl YknKucUQo5Yp/fGaN+jGImu45E4ZDlVgntE7qw32BP5fl2xwWKUHIq+laW92GXd0Y5W6O+ 9f8VfIxoCb+/pqjoO1HMw5wdyVChvXnyMre7kDdvxOVtELsPxPJ9/deli5pDSw== From: Miquel Raynal To: "Rabara, Niravkumar L" Cc: Richard Weinberger , Vignesh Raghavendra , "linux@treblig.org" , Shen Lichuan , Jinjie Ruan , "u.kleine-koenig@baylibre.com" , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: Re: [PATCH v2 1/3] mtd: rawnand: cadence: support deferred prob when DMA is not ready In-Reply-To: (Niravkumar L. Rabara's message of "Thu, 30 Jan 2025 03:51:08 +0000") References: <20250116032154.3976447-1-niravkumar.l.rabara@intel.com> <20250116032154.3976447-2-niravkumar.l.rabara@intel.com> <87plkgpk8k.fsf@bootlin.com> <874j1i0wfq.fsf@bootlin.com> User-Agent: mu4e 1.12.7; emacs 29.4 Date: Thu, 30 Jan 2025 16:19:53 +0100 Message-ID: <87msf8z5uu.fsf@bootlin.com> MIME-Version: 1.0 X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdeiudeiucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufgjfhgffffkgggtgfesthhqredttderjeenucfhrhhomhepofhiqhhuvghlucftrgihnhgrlhcuoehmihhquhgvlhdrrhgrhihnrghlsegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpeffgefhjedtfeeigeduudekudejkedtiefhleelueeiueevheekvdeludehiedvfeenucfkphepledtrdekledrudeifedruddvjeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeeltddrkeelrdduieefrdduvdejpdhhvghloheplhhotggrlhhhohhsthdpmhgrihhlfhhrohhmpehmihhquhgvlhdrrhgrhihnrghlsegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopedutddprhgtphhtthhopehnihhrrghvkhhumhgrrhdrlhdrrhgrsggrrhgrsehinhhtvghlrdgtohhmpdhrtghpthhtoheprhhitghhrghrugesnhhougdrrghtpdhrtghpthhtohepvhhighhnvghshhhrsehtihdrtghomhdprhgtphhtthhopehlihhnuhigsehtrhgvsghlihhgrdhorhhgpdhrtghpthhtohepshhhvghnlhhitghhuhgrnhesvhhivhhordgtohhmpdhrtghpthhtoheprhhurghnjhhinhhji hgvsehhuhgrfigvihdrtghomhdprhgtphhtthhopehurdhklhgvihhnvgdqkhhovghnihhgsegsrgihlhhisghrvgdrtghomhdprhgtphhtthhopehlihhnuhigqdhmthgusehlihhsthhsrdhinhhfrhgruggvrggurdhorhhg X-GND-Sasl: miquel.raynal@bootlin.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250130_072000_375644_9ADEF14B X-CRM114-Status: GOOD ( 21.65 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; 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Rabara's message of "Thu, 30 Jan 2025 03:51:08 +0000") References: <20250116032154.3976447-1-niravkumar.l.rabara@intel.com> <20250116032154.3976447-2-niravkumar.l.rabara@intel.com> <87plkgpk8k.fsf@bootlin.com> <874j1i0wfq.fsf@bootlin.com> User-Agent: mu4e 1.12.7; emacs 29.4 Date: Thu, 30 Jan 2025 16:19:53 +0100 Message-ID: <87msf8z5uu.fsf@bootlin.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdeiudeiucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufgjfhgffffkgggtgfesthhqredttderjeenucfhrhhomhepofhiqhhuvghlucftrgihnhgrlhcuoehmihhquhgvlhdrrhgrhihnrghlsegsohhothhlihhnrdgtohhmqeenucggtffrrghtthgvrhhnpeffgefhjedtfeeigeduudekudejkedtiefhleelueeiueevheekvdeludehiedvfeenucfkphepledtrdekledrudeifedruddvjeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeeltddrkeelrdduieefrdduvdejpdhhvghloheplhhotggrlhhhohhsthdpmhgrihhlfhhrohhmpehmihhquhgvlhdrrhgrhihnrghlsegsohhothhlihhnrdgtohhmpdhnsggprhgtphhtthhopedutddprhgtphhtthhopehnihhrrghvkhhumhgrrhdrlhdrrhgrsggrrhgrsehinhhtvghlrdgtohhmpdhrtghpthhtoheprhhitghhrghrugesnhhougdrrghtpdhrtghpthhtohepvhhighhnvghshhhrsehtihdrtghomhdprhgtphhtthhopehlihhnuhigsehtrhgvsghlihhgrdhorhhgpdhrtghpthhtohepshhhvghnlhhitghhuhgrnhesvhhivhhordgtohhmpdhrtghpthhtoheprhhurghnjhhinhhji hgvsehhuhgrfigvihdrtghomhdprhgtphhtthhopehurdhklhgvihhnvgdqkhhovghnihhgsegsrgihlhhisghrvgdrtghomhdprhgtphhtthhopehlihhnuhigqdhmthgusehlihhsthhsrdhinhhfrhgruggvrggurdhorhhg X-GND-Sasl: miquel.raynal@bootlin.com Hello, >> > Driver works without external DMA interface i.e. has_dma=3D0. >> > However current driver does not have a mechanism to configure it from >> > device tree. >>=20 >> What? Why are you requesting a DMA channel from a dmaengine in this case? >>=20 >> Please make the distinction between the OS implementation (the driver) a= nd >> the DT binding which describe the HW and only the HW. >>=20 > > Let me clarify from bindings(hw) and driver prospective.=20 > > Bindings :- > Cadence NAND controller HW has MMIO registers, so called slave DMA interf= ace > for page programming or page read.=20 > reg =3D <0x10b80000 0x10000>, > <0x10840000 0x10000>; > reg-names =3D "reg", "sdma"; // sdma =3D Slave DMA data port reg= ister set > > It appears that dt bindings has captured sdma interface correctly. Slave DMA is very confusing because in Linux we make the distinction between: 1- external DMA (generic DMA controller) driven through the dmaengine API, through which we interact using the so called slave API 2- peripheral DMA (DMA controller embedded in the NAND IP) when there is no "external/generic" engine. In this case we control DMA transfers using the registers of the NAND controller (or a nearby range, in this case), the same driver handles both the NAND and the DMA part. You used the wording Slave DMA (#1), but it feels like you are talking about the other (#2). Can you please confirm in which case we are? > Linux Driver:- > Driver can read these sdma registers directly or it can use the DMA. > Existing driver code has hardcoded has_dma with an assumption that > an external DMA is always used and relies on DMA API for data > transfer. I am sorry but DMA API does not mean much. There are 3 APIs: - dma-mapping, for the buffers and the coherency - dmaengine, used in case #1 only, to drive the external DMA controllers - dma-buf to share buffers between areas in the kernel (out of scope) > Thant is why it requires to use DMA channel from dmaengine. If I understand it right, no :-) Either you have an external DMA controller (#2) or an internal one (#1) but in this second case there is no DMA channel request nor any engine-related API. Of course you need to use the dma-mapping API for the buffers. > In my previous reply, I tried to describe this driver scenario but maybe = I mixed up.=20 > has_dma=3D0, i.e. accessing sdma register without using dmaengine is > also working. But do you have an external DMA engine in the end? Or is it specific to the NAND controller? > However, currently there is no option in driver to choose between using d= maengine and > direct register access. > Thanks, Miqu=C3=A8l