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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95914C43381 for ; Tue, 19 Feb 2019 09:49:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 606B22146E for ; Tue, 19 Feb 2019 09:49:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="q50igjyU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727203AbfBSJtd (ORCPT ); Tue, 19 Feb 2019 04:49:33 -0500 Received: from mail-lj1-f194.google.com ([209.85.208.194]:35129 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726289AbfBSJtd (ORCPT ); Tue, 19 Feb 2019 04:49:33 -0500 Received: by mail-lj1-f194.google.com with SMTP id j13-v6so16885336ljc.2 for ; Tue, 19 Feb 2019 01:49:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ceFCSGNoNWqq4YNDYdMfd0R6+0aefkkTFSwlzn3bDMc=; b=q50igjyUXGTbdP2dtEYYaPbL4i99WirmmzhAVPlv+S+XTrjQcDAXaMgNCRwlqI2p1h kFynGICCSdYbQEvpCzsdJ+ycZ8h2z5VGSecilLwhHCcPE4rDhm7NjDPy6h30bkgGpSPR LmkVbvKagfs7bp/KyqpSQ5peufL01o9bHLTY9TZ5s0RHAW0Db1ISTGIL6gVka+q9dc+h DCjkm/PKWBk/2oLr7axonWKyT9BWPgoU+egZoGWt5bQWmYHPco9Qt7kpPBdFKD5nqgel 7LPfX3YreztHtnN9jOsP0iLvT86XUQx5caJ7Jvufpy1aggKZ0884pJz5eKQOxHqinTRN jErQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ceFCSGNoNWqq4YNDYdMfd0R6+0aefkkTFSwlzn3bDMc=; b=VmEqVPm8S9nyeDog0ycakrz2lH3UVLNaJlxyOEHJSfQE0esB3JorjQbDHo/eXvn1kJ 06p3G2/qhp8CJFZiEZ480Mstt8wdIW2vcxto5KGqKueInD7kIHGv7Qh3M0oe0sx1qTfV T59/VyIAY21oUMx3SNokrCNSe0YbvtOWxMWB3vcA3+6FiTglMU5gZ/LIrDQ7RHkCnGki 2PEnESIZB6iyMj4GkfbiLVAloZRZ1mjCy2t+vjMA31UhM3pH8kD409lr9Pa//35Ybx6D CJk1NHzGOwBqUiov+wc2tU+sFSvzNtbmwbHPre2wMWkB5O9pHZNknh8Pn8VrhBiLNU5x oQ0Q== X-Gm-Message-State: AHQUAuZsAXqwUhRyJVMnBGoRisxLKfK3RIPzPhJrMAHSpLyOUOn6v4zL WEyXQjw2whGrKssteuWJmvlq7mlZK4TAVTy7+ckuWQ== X-Google-Smtp-Source: AHgI3IYsae3AMyaa7jkN8e9h6ArVPBkR535/IDlsxe3Uwr0X0LXfFZ6l+PcQHAeYndpX5oPVjC1VymuTR5sD0VSszj0= X-Received: by 2002:a2e:251:: with SMTP id 78mr11030225ljc.90.1550569770704; Tue, 19 Feb 2019 01:49:30 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Baolin Wang Date: Tue, 19 Feb 2019 17:49:19 +0800 Message-ID: Subject: Re: [PATCH 1/3] dt-bindings: dmaengine: Add one new cell to present hardware slave id To: Geert Uytterhoeven Cc: Arnd Bergmann , Vinod Koul , Rob Herring , Mark Rutland , Olof Johansson , Orson Zhai , Lyra Zhang , Dan Williams , DTML , arm-soc , Linux ARM , Linux Kernel Mailing List , dmaengine@vger.kernel.org, eric.long@unisoc.com, Mark Brown Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Geert, On Tue, 19 Feb 2019 at 17:30, Geert Uytterhoeven wrote: > > Hi Baolin, > > On Tue, Feb 19, 2019 at 4:15 AM Baolin Wang wrote: > > On Mon, 18 Feb 2019 at 20:23, Arnd Bergmann wrote: > > > On Mon, Feb 18, 2019 at 11:52 AM Baolin Wang wrote: > > > > On Mon, 18 Feb 2019 at 18:31, Arnd Bergmann wrote: > > > > > > > > > > On Tue, Feb 12, 2019 at 9:25 AM Baolin Wang wrote: > > > > > > On Fri, 1 Feb 2019 at 19:53, Baolin Wang wrote: > > > > > > > On Thu, 31 Jan 2019 at 00:52, Arnd Bergmann wrote: > > > > > > > > On Tue, Jan 22, 2019 at 2:21 PM Baolin Wang wrote: > > > > > > > > > > > > > > > > > > Client: > > > > > > > > > DMA clients connected to the Spreadtrum DMA controller must use the format > > > > > > > > > -described in the dma.txt file, using a two-cell specifier for each channel. > > > > > > > > > -The two cells in order are: > > > > > > > > > +described in the dma.txt file, using a three-cell specifier for each channel. > > > > > > > > > +The three cells in order are: > > > > > > > > > 1. A phandle pointing to the DMA controller. > > > > > > > > > 2. The channel id. > > > > > > > > > +3. The hardware slave id which is used for clients to trigger DMA engine > > > > > > > > > +automatically. > > > > > > > > > > > > > > > > I notice that this is an incompatible binding change. Is that necessary? > > > > > > > > If the current code works, I'd suggest allowing both #dma-cells=<2> > > > > > > > > and <3>, and then implementing both in the driver. > > > > > > > > > > > > > > Yes, this is necessary. > > > > > > > > > > > > > > Yes, current code can work, but the problem is that the DMA clients > > > > > > > must add one property (something like "sprd,slave-id") to specify the > > > > > > > slave id. So considering this, we want to change the dma-cells to 2, > > > > > > > including dma channel and dma slave id, which can avoid introducing > > > > > > > some similar properties for DMA clients. > > > > > > > > > > > > > > Now there are no DMA clients in mainline for Spreadtrum platform, and > > > > > > > we want to upstream our first DMA clients: SPI controller. So no other > > > > > > > drivers need to change when we changing dma cells. Thanks. > > > > > > > > > > > > Do you have any other concerns about this patch set? If not, I think > > > > > > Vinod can apply this patch set. Thanks. > > > > > > > > > > Sorry for the late reply. Yes, this makes sense since there are no > > > > > existing users then. For the DT changes going through the dmaengine > > > > > tree > > > > > > > > > > Acked-by: Arnd Bergmann > > > > > > > > Thanks for your reviewing. > > > > > > > > > > > > > > One more question, to make sure we don't need to edit it again: > > > > > Why do you need both a 'channel id' and a 'slave id' here? Is this > > > > > a strict hardware requirement for your DMA engine? In many > > > > > other designs, only a DMA request line number needs to > > > > > be described, and I think this would correspond to what you > > > > > call the 'hardware slave id' in your documentation. > > > > > > > > I try to explain why we need the slave id. > > > > > > > > For our DMA engine driver, we have software request mode and hardware > > > > request mode. For software request mode, the DMA engine driver need > > > > trigger DMA to start transfer manually. But for hardware request mode, > > > > we just set one unique slave id corresponding to the slave hardware to > > > > the DMA engine, then the slave hardware can trigger DMA automatically. > > > > And the slave id is not always same with the channel id according to > > > > the SoC design, so we add one cell to specify the slave id. > > > > > > I did understand the need for a slave-id, I was instead wondering about > > > the channel-id number. On many SoCs, all channels are equal, and you > > > just have to pick one of those with the right capabilities for a particular > > > slave. > > > > Yes, all channels are equal. We just set a unique slave id for the > > channel for a particular slave. For example, the SPI slave can use > > channel 10 for tx transfer by setting slave id 11, or it also can use > > channel 9 for tx transfer by setting same slave id 11. > > So the channel selection is software policy, not hardware description, and > thus doesn't belong in DT? > > Can't the DMA engine driver allocate channels dynamically, removing the > need to specify this in DT? In theory we can do as you suggested. But we still want to manage/assign the DMA channel resources manually for one SoC, we can make sure some important DMA slaves (such as audio) can request a DMA channel at runtime firstly, another benefit is that it is easy to debug since we can easily know which channel is assigned for this slave. -- Baolin Wang Best Regards