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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 2EFA6C433E1 for ; Tue, 7 Jul 2020 11:21:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1008120702 for ; Tue, 7 Jul 2020 11:21:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594120911; bh=LCXyDHmTACa91oTt6HIAuKnB5ZBvshX1CUGP0YfokcA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=oaaUzGc0S9VB/L0jyKoDllw9OkBHSuPjj1p+VPc/XyZfwZLIwGVNGfTWaHnB6lCcR g++wsvhqyoD/CtwaNIziDf4NT0TXn4N2Xun9jqqoNAm+dQxvKjWw/HDlbgYoGzP0Hb JuoBxlAHi040gmj9ce1jziqtghdtwO84nYmhSEO8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728183AbgGGLVu (ORCPT ); Tue, 7 Jul 2020 07:21:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:36732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726805AbgGGLVt (ORCPT ); Tue, 7 Jul 2020 07:21:49 -0400 Received: from localhost (fw-tnat.cambridge.arm.com [217.140.96.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 533D3206CD; Tue, 7 Jul 2020 11:21:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594120908; bh=LCXyDHmTACa91oTt6HIAuKnB5ZBvshX1CUGP0YfokcA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Kf0k8NwYKTwSPgXD/+u13NKY+MI2lSJc8Dhy8uBT0QGrOsRZxpiEENGd6VwYuaAP4 Og+T5dw06LVk8ngqh4ov/N1211OKU08qIk/GQjjKrjFdlJ2vNWCSCyWvA5VH31wfcI HyakBUEcls7b0cFcLewMalppZAuDtY+WrInb7wVc= Date: Tue, 7 Jul 2020 12:21:44 +0100 From: Mark Brown To: Adrian Fiergolski Cc: geert@linux-m68k.org, lukas@wunner.de, kernel test robot , Rob Herring , linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] spi: Add the SPI daisy chain support. Message-ID: <20200707112144.GH4870@sirena.org.uk> References: <202007040833.xIqR5rAw%lkp@intel.com> <20200706092247.20740-1-adrian.fiergolski@fastree3d.com> <20200706161810.GB6176@sirena.org.uk> <0072bb03-d6ec-38b8-0c31-61571b77bf93@fastree3d.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="X1xGqyAVbSpAWs5A" Content-Disposition: inline In-Reply-To: <0072bb03-d6ec-38b8-0c31-61571b77bf93@fastree3d.com> X-Cookie: I hate dying. User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --X1xGqyAVbSpAWs5A Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jul 07, 2020 at 12:53:38PM +0200, Adrian Fiergolski wrote: > On 06.07.2020=A018:18, Mark Brown wrote: > > On Mon, Jul 06, 2020 at 11:22:43AM +0200, Adrian Fiergolski wrote: > > this. Perhaps this needs to be a library for devices that can daisy > > chain? It does feel like the instances should be aware of each other > > since half the point with building the hardware like this is that it > > enables operations on multiple devices to happen in sync. > Well, I assume that one can connect completely different SPI devices on > a single daisy chain. In order to address all devices in a single > access, a controller would need to delay a transaction, wait for a > certain moment (how long?), synchronise and then transfer the message. I > think it adds unnecessary complexity, as MHO many engineers' issue at I'd imagine something more like regmap's explicit management with pausing and unpausing transactions (indeed regmap might be a good mechanism for this for devices with a register map) would not be that cumbersome to use. Pause, set the desired target state and then sync that state out to the hardware. This isn't something that can sensibly be done at the controller level, the devices do need to be aware of what's going on, which is why I'm saying that there's a need for the devices to be aware of things. --X1xGqyAVbSpAWs5A Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAl8EWscACgkQJNaLcl1U h9C9CAf/RCKRB0Hy7tmjHtb+eFWn8xEg0QykkkMX2+o03ZcMFdr81ycG2RWsJADv Rj64p7v42qb4f7xhn2HTNpbxV+kLasRIUWJmAloPPhLomUzxHP3NStyqaRf0Ts+G lvDA4oDzYAulv7SO03//M9p4qv4P2xAXKRKpO7O8YYWU5sx8r7OssJZhUdyEnqLG l/EMPP/nRXODodaQiMz60ZtDUb6hmIGYhKeI3tCFiatjFhGb9vKZSQdiInNlZLI8 mYldBLQQe1cGpOaEI5BHt/KyJSDLkmHjVK1lyczD+1ksSY0OZpHjAxAoeHDexNpq hd9q0OOhSNO6Cz9o0+B/MOd7nYMY2Q== =in23 -----END PGP SIGNATURE----- --X1xGqyAVbSpAWs5A--