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 4B637C433F5 for ; Tue, 29 Mar 2022 15:32:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236836AbiC2Pdt (ORCPT ); Tue, 29 Mar 2022 11:33:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238781AbiC2PdK (ORCPT ); Tue, 29 Mar 2022 11:33:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D05F1207EC; Tue, 29 Mar 2022 08:31:26 -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 2C19B60EDF; Tue, 29 Mar 2022 15:31:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49EFEC2BBE4; Tue, 29 Mar 2022 15:31:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1648567885; bh=YEzE/YcpvqqkcMmxUt5/89JnyfIyasWtNCTkrpB/nTQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nGliDUx1XpLBTY+M1+jN/YhNuNDMIM4RV751BM/0ANbsgCKbza8Gehf6xf8u613Rq 7fpofgTcZUopDwAS6kDSwxkKv2OFfqz+0lawL/vcw7Ap0vjmK0a53DEf1xO+LwVF/j 6DNqkFAis10JEUtSzt+QjaSTSzYM64fD3EEKkgvjFPLnoCZfRCRS8JR9k6zLFzE66k uqznO/ah1xpYmcjNm1mBm695rxfYXDKptHbdr6faQBaXCy8+Rk0vZK8qDx+/SjHNug LKob2/v5EEGNS7KVGP5bPFwM7MIxNj8apHaIm+IFh8N3UtE2tNtNfUmwSEpY8cbLv/ yDEnIbazRlQNA== Date: Tue, 29 Mar 2022 21:01:14 +0530 From: Manivannan Sadhasivam To: Yann Gautier Cc: Linus Walleij , Rob Herring , Ulf Hansson , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, Alexandre Torgue , Christophe Kerello , Ludovic Barre , Maxime Coquelin , Philipp Zabel , Russell King , Marek Vasut , kernel@dh-electronics.com, Grzegorz Szymaszek Subject: Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA LLI Message-ID: <20220329153114.GA58120@thinkpad> References: <20220304135134.47827-1-yann.gautier@foss.st.com> <20220304135134.47827-2-yann.gautier@foss.st.com> <0bc53018-fce4-4104-fa47-6e60d2367d69@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0bc53018-fce4-4104-fa47-6e60d2367d69@foss.st.com> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, Mar 15, 2022 at 09:26:01AM +0100, Yann Gautier wrote: > On 3/14/22 23:43, Linus Walleij wrote: > > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier wrote: > > > > > On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported > > > starting from revision v2 of the peripheral. But it has limitations, > > > as all the buffers should be aligned on block size (except the last one). > > > But this cannot be guaranteed with SDIO. We should then have a property > > > to disable the support of LLI. > > > > > > Signed-off-by: Yann Gautier > > > > Actually I think this is present also on the ux500 variants. See: > > commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 > > "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" > > > > Spot the variant data "dma_power_of_2". > > > > So whatever property you add > > to the variant data (not in the device tree please) should > > be added to the ux500 variants as well, it will *VERY* likely > > have a problem with LLI elements not being a power of 2 > > as it is the ancestor of later STMicro variants. > > > > It might actually be the reason for some annoying WiFi error > > messages I have seen :/ > > > > Yours, > > Linus Walleij > > Hi Linus, > > The STM32 variant uses an internal DMA, and the DMA functions are in its > dedicated file. So I was planning to do the same as what is done in > meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA > constraints are not fulfilled. Not sure it can help for Ux500. > Irrelevant to this patch: May I know why the internal DMA cannot be represented as a dmaengine driver? We started seeing these internal DMA implementations in the other subsystems as well with pointers towards MMC core [1]. Thanks, Mani [1] https://lore.kernel.org/all/CA+V-a8tfUgvzPyMe_FHuz=8mmC6dPHP7E=e+nCzOey04vCcAkg@mail.gmail.com/ > Ulf, before I send my new series (although it is not ready yet), would you > be OK with the bounce buffer idea? > > > Best regards, > Yann