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 9596ED1F9DA for ; Tue, 15 Oct 2024 21:32:37 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=TqIByzgwVOWwCnn6llRc7MDXxQkConB3OY/jUxC3P7k=; b=sRxsADacCksq7HbqvqDixoSp6M mWqOxo10dZpxuTwq9+UcIhbkW9gr1Zgs3iIpB+sjHtX7npwsty/FawExJGjvh57mYcMqvPCtGwaST dqVb59fY7ubY1V79RT0zjzlm6/J6rLk/CriRHx9DAxNSx6rNI5Yumx+wM9KKrbwQ5nKrWwMXrRo0F 9ooqlCusQRsm5OW4DxnJkaqE1KhL6iKd1Jxvc6Oprp+klhBQKohG1TpuFDzitdG2rtljZy0RmWvwK pwf4tPWbo+3d12xsYWZkem/gfd556nmzY3pQNC/MSq7oHyXJeNtfSkP4opgiP0LcyL9CRaKuNTzld 40LJuf/A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t0p9V-00000009eZL-2Ato; Tue, 15 Oct 2024 21:32:25 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t0p83-00000009e8Y-2JTv for linux-arm-kernel@lists.infradead.org; Tue, 15 Oct 2024 21:30:57 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 6FB705C5F17; Tue, 15 Oct 2024 21:30:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E940C4CEC6; Tue, 15 Oct 2024 21:30:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729027854; bh=U7XE5u0pRR0pjYvZzMuh+uJeZUztv2GjXrvRNqavzVs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TwZuXoGBhtKmtnUGkO9xhM+OkaS9RCQXoW1EB2LgyL+yZks5KwPMA3TkdudxYKAT6 N7Fbp+l2LfaBB1gbBDmJZ3n97fnpu/SVZIDwSw02u+nA+/AxJiA7iv5EGQxutMkpNk WfGRBQWhKzGlehhRjbyCfstJtjq48xsNR0DNnZA+L31+WSZRUwXioxeqHUlDRIZ76G KA52D7nTrumkV9YhnLUtxGk3Dewd+LKyXFAt7l/2a78sk/4FWo9yYbtey2P0JR3vi8 wKqlN916tSBZdEamcVw3Xgt4t+EW4V6i/QpH3Ew1SKMWa4UmLnodB92b5KiWEys1cP jSa/R3fVTwFng== Date: Tue, 15 Oct 2024 16:30:53 -0500 From: Rob Herring To: Amelie Delaunay Cc: Vinod Koul , Krzysztof Kozlowski , Conor Dooley , Maxime Coquelin , Alexandre Torgue , dmaengine@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/9] dt-bindings: dma: stm32-dma3: prevent additional transfers Message-ID: <20241015213053.GA1992090-robh@kernel.org> References: <20241015-dma3-mp25-updates-v2-0-b63e21556ec8@foss.st.com> <20241015-dma3-mp25-updates-v2-4-b63e21556ec8@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241015-dma3-mp25-updates-v2-4-b63e21556ec8@foss.st.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241015_143055_657427_ABD1C806 X-CRM114-Status: GOOD ( 18.30 ) 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 On Tue, Oct 15, 2024 at 02:14:40PM +0200, Amelie Delaunay wrote: > stm32-dma3 driver refactors the linked-list in order to address the memory > with the highest possible data width. You are still talking about driver... > It means that it can introduce up to 2 linked-list items. One with a > transfer length multiple of channel maximum burst length and so with the > highest possible data width. And an extra one with the latest bytes, with > lower data width. > Some devices (e.g. FMC ECC) don't support having several transfers instead > of only one. > So add the possibility to prevent these additional transfers, by setting > bit 17 of the 'DMA transfer requirements' bit mask. Some devices require single transfers. That's about all you need to say. > > Signed-off-by: Amelie Delaunay > --- > Changes in v2: > - Reword commit title/message/content as per Rob's suggestion. > --- > Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml > index 5484848735f8ac3d2050104bbab1d986e82ba6a7..36f9fe860eb990e6caccedd31460ee6993772a35 100644 > --- a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml > +++ b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml > @@ -99,6 +99,9 @@ properties: > -bit 16: Prevent packing/unpacking mode > 0x0: pack/unpack enabled when source data width/burst != destination data width/burst > 0x1: memory data width/burst forced to peripheral data width/burst to prevent pack/unpack > + -bit 17: Prevent additional transfers due to linked-list refactoring > + 0x0: don't prevent additional transfers for optimal performance > + 0x1: prevent additional transfer to accommodate user constraints such as single transfer > > required: > - compatible > > -- > 2.25.1 >