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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_MUTT 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 89A07C04AB3 for ; Mon, 6 May 2019 07:38:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51B192087F for ; Mon, 6 May 2019 07:38:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557128285; bh=DOKRU8VF11kW1JPbXVxEGEopd7AYRSbPKW251llYHbY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=HkEWbU0q5qnL0dGbO8KAe+38+W7TK+L7F8EUdx5So8Bquv2paNsXE84bA7M/jV55F K2KtgjiZYz2mS4849F4aUyqrMBzwI7VtbJULf/RdBrheyjkH9GfVU7jfRgeoSNWd8T HK6G3dJJjtDpk+kmBf/XTx4yGutaUn0MQtJxFlAE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726486AbfEFHiE (ORCPT ); Mon, 6 May 2019 03:38:04 -0400 Received: from heliosphere.sirena.org.uk ([172.104.155.198]:38980 "EHLO heliosphere.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726346AbfEFHhr (ORCPT ); Mon, 6 May 2019 03:37:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sirena.org.uk; s=20170815-heliosphere; h=In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=tHEGQ9oW3tTgBWCAOeQCOTnFuPn94mh9AkAln7vInY4=; b=l7fNRNLCq2MIuMeUy6SV4mr7n 1qpPp/FUVJ51Os8GeDRVf7F5aguVa/b0irPfvM9G/cW6+FEzAtdo798HVEHAhauYXY8UsPSnZQSRL tJ1EDC287NTk/V18FW2MzFdOSlzo/2DhR2TkqiYxz8p9y7lM+asUSwmonZ5IO7jxu/sL8=; Received: from kd111239184067.au-net.ne.jp ([111.239.184.67] helo=finisterre.ee.mobilebroadband) by heliosphere.sirena.org.uk with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hNYBx-0000rz-7U; Mon, 06 May 2019 07:37:42 +0000 Received: by finisterre.ee.mobilebroadband (Postfix, from userid 1000) id 5653E44003B; Mon, 6 May 2019 05:44:25 +0100 (BST) Date: Mon, 6 May 2019 13:44:25 +0900 From: Mark Brown To: Sowjanya Komatineni Cc: "thierry.reding@gmail.com" , Jonathan Hunter , Timo Alho , "robh+dt@kernel.org" , "mark.rutland@arm.com" , Krishna Yarlagadda , Laxman Dewangan , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-spi@vger.kernel.org" , "devicetree@vger.kernel.org" Subject: Re: [PATCH V3 5/9] spi: export spi core function spi_set_cs Message-ID: <20190506044425.GN14916@sirena.org.uk> References: <1555363834-32155-1-git-send-email-skomatineni@nvidia.com> <1555363834-32155-6-git-send-email-skomatineni@nvidia.com> <20190419151823.GS2803@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="UIkw8Cc2/Xz5YwHB" Content-Disposition: inline In-Reply-To: X-Cookie: -- I have seen the FUN -- 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 --UIkw8Cc2/Xz5YwHB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Apr 29, 2019 at 10:02:46PM +0000, Sowjanya Komatineni wrote: Please fix your mail client to word wrap within paragraphs at something substantially less than 80 columns. Doing this makes your messages much easier to read and reply to. > > On Mon, Apr 15, 2019 at 02:30:30PM -0700, Sowjanya Komatineni wrote: > > > This patch exports spi_set_cs of the spi core to allow SPI masters to= =20 > > > use when gpio based chip select is needed. > > This isn't really what I meant when I said it'd be good to use the > > core GPIO code - this function doesn't do a huge amount really and > > the usage of it in your subsequent patch for the > driver isn't > > exactly joined up with the little it does (which is mainly swapping > > in the GPIO chip select instead of the hardware chip select) isn't > > used in your driver usage of this as far as I can see. The bulk of > > the chip select handling code in the core is actually in > > transfer_one_message() which your driver doesn't use as it's got > > it's own implementation of that; I've not looked in enough detail to > > figure out if it could use it. > In SPI Tegra driver, we wanted to have GPIO based CS control when > cs-gpios is specified in parallel to HW/SW CS. Having parallel GPIO > based CS is to mimic some of the timing stuff that's needed for some > spi devices by not actually using HW CS on platform but only for SPI > HW design logic inside the chip. > Tegra spi driver don't use set_cs callback so looking into spi_set_cs > from spi core implementation when cs-gpios property is used it exactly > the same that is needed for GPIO control CS. So used this in V3.=20 > Can you please provide more details on what you are suggesting? > Do you prefer not to use SPI core spi_set_cs and gpio_set_values APIs > and instead implement in tegra SPI driver using GPIO descriptors ? You're probably best open coding in the driver if there's value in using the hardware chip select. --UIkw8Cc2/Xz5YwHB Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAlzPu6YACgkQJNaLcl1U h9DM0Qf7Bykvbj1t4ndVRPemN1ZjRrYC94F5FOwPPHuLYIIFawPR0xupsoIwdZPi b9rbj7/L3dNBHHO+gjkDEQLYC++gMNJnL5bSo2AA8cz/qJhVqzMS0nu+F6Fgofup jwo4IWbjxYPAJWqrjWFj6Y79h+cXTmu+lcOiEnHoEjuqjxNH5fWJXqLrDYe7irOJ ST8QQXWtz2T1A9BfvWzZ56NFlieoOR+vKQFZZjwYzS7irq+F9LqT5Q/VKNQOvExL SLu4ZnMlPuZQBkOxFqtr8yve31kkxhyFfUrvhKCBwAHKzg+dt3Aop+gkbwJCeEEJ tuLSjnUOUENVdEKWAwHEj4DdEcXH7Q== =C76I -----END PGP SIGNATURE----- --UIkw8Cc2/Xz5YwHB--