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 C64EBC43334 for ; Fri, 15 Jul 2022 16:03:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231342AbiGOQDm (ORCPT ); Fri, 15 Jul 2022 12:03:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229778AbiGOQDj (ORCPT ); Fri, 15 Jul 2022 12:03:39 -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 6D442FC8; Fri, 15 Jul 2022 09:03:38 -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 0C6636216E; Fri, 15 Jul 2022 16:03:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66131C34115; Fri, 15 Jul 2022 16:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657901017; bh=jrlFeUIlmq6USCDUyOFysJvOq822JHFZZ7Z40MxY9qw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dadoHH8CNpbJL21+f44Epd5J674JaHKpzitYi5Yt6EmFV684hfkDRo+FU0AUmtQqS z1+Hz1CQ6Pw7Y+OIeVoXKvDwcNmTI/60tTPCQ8DFUG/j8lkQnjDvcE94j18yHU/By2 Phhwo4EiJ/3/rQz9AuknKwC9JQR0+oZh5Yls6JEYUch/QOKB1zjBpeTlsPpc3MAnEK WQ1wuH8tWlBKZemmAsiWSaQW3jCKJAkMbHD6WfEpsc7lryOKiga4QG0/3uAqnFeGgF pKQuDymcNVqLw8AZQNAgogELOmcLaCvQoV/n3JomfnruEUbYSGz9jwTWulu9U4d4yp ETqG4+zPC0Crw== Date: Fri, 15 Jul 2022 17:03:31 +0100 From: Mark Brown To: "Mahapatra, Amit Kumar" Cc: Michal Simek , Amit Kumar Mahapatra , Krzysztof Kozlowski , "p.yadav@ti.com" , "miquel.raynal@bootlin.com" , "richard@nod.at" , "vigneshr@ti.com" , "git@xilinx.com" , "linux-spi@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "michael@walle.cc" , "linux-mtd@lists.infradead.org" , "git (AMD-Xilinx)" Subject: Re: [RFC PATCH 1/2] spi: Add multiple CS support for a single SPI device Message-ID: References: <20220606112607.20800-1-amit.kumar-mahapatra@xilinx.com> <20220606112607.20800-2-amit.kumar-mahapatra@xilinx.com> <40110ff8-5c19-bc54-759b-a51a919788eb@xilinx.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="DxORmGk94Y1lYeUm" Content-Disposition: inline In-Reply-To: X-Cookie: You dialed 5483. Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --DxORmGk94Y1lYeUm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jul 15, 2022 at 03:36:23PM +0000, Mahapatra, Amit Kumar wrote: > Thank you for the clarification. > As per my understanding we would not be needing a new DT=20 > property for expressing multi chip select support in the driver. > We can use "num-cs" property of the spi controller for=20 > broadcasting multi chip select support of the driver. > If "num-cs" value is greater than 1 then the driver can support=20 > multiple chip selects. That's true in some sense but not in the sense of being actually able to use more than one chip select for a single device. If the controller hardware manages the chip selects it may not be physically possible for it to control more than one chip select. While it's not an issue for the bindings even hardware that can physically do it is going to need a driver update (in the core for GPIO stuff) to do so. --DxORmGk94Y1lYeUm Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmLRj9IACgkQJNaLcl1U h9ASdQf/ca/l2sFbQii/WohGkZhhQqY8tP78zj73reO3O08IgMatkP91Qg1cm/g4 C9lTmIC/jAtn3id4aXNkli7H7ZJhq8dOfzd+O5T32FIULoAvLJUnyw6roTsncRul RUooo3/llgKSEX9sZ3w/nfOoyBg49Sj/n6hkxuvIIj33Cys2E8y5JzXiVbEyFCkh Q9amQxSAa4p+jyDj4zQ1MtY4J58LsepXJkU+E1F/8HuJHieKxChblZKC4LCGwZ2k UWVdCUxSTg25IpkLJLrjbJBRuwuwJl9ZGTeDj78Sf9OM/x1vbkgKPwk5RVGioKMV vWkEa2d0/0ioERCpoUjzCYH27X8bxg== =AYb4 -----END PGP SIGNATURE----- --DxORmGk94Y1lYeUm--