From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH 1/2] dt-bindings: spi: dw: add cs-override property Date: Wed, 10 Oct 2018 12:27:53 +0100 Message-ID: <20181010112753.GC6294@sirena.org.uk> References: <1539155293-21750-1-git-send-email-talel@amazon.com> <20181010101825.GA6294@sirena.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="XWOWbaMNXpFDWE00" Cc: linux-spi@vger.kernel.org, robh+dt@kernel.org, mark.rutland@arm.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, ronenk@amazon.com, barakw@amazon.com, David Woodhouse To: Talel Shenhar Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org --XWOWbaMNXpFDWE00 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Oct 10, 2018 at 02:23:40PM +0300, Talel Shenhar wrote: > On 10/10/2018 01:18 PM, Mark Brown wrote: > > On Wed, Oct 10, 2018 at 10:08:12AM +0300, Talel Shenhar wrote: > >> The dw spi controller has an auto-deselect of Chip-Select, in case there is > >> no data inside the Tx FIFO. While working on platforms with Alpine chips, > > Why would we ever want to use this behaviour? It will be broken for any > > non-trivial SPI message such as those made with multiple transfers > > anyway. Why not just unconditionally control it manually? > This behavior (auto-deselect of Chip-Select) is the default behavior of dw spi controller hw. > On Alpine chip there is additional behavior added to the dw spi controller hw that allows the sw to disable this behavior. > This patch allows the dw driver to enable this hw workaround and add the needed sw manual control for it. If this is a modified IP with additional features then it should be given a new compatible string rather than having a property - it's not just configuration of the existing IP, it's a new thing and we may find there are other quirks that have to be taken care of for it. --XWOWbaMNXpFDWE00 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAlu94jgACgkQJNaLcl1U h9ApoQf/bZoqz6AzEschlNCke1wLPI98oWSDZLffCSfz9cw1bkrYYqkHInTWRcH6 kDWI4TUt7/y/Vfe2KZOB5B14B05XJh5y4NB21zLNc7BQCbmY1TPNHKb4Q/ums5qp cPnz+jyFf2wUrRBsu9MZ6G5LbwameBAjy0aw1YlIzvtMHovsT1TCoAcazwCWrZoD 5oe0ZTvJ5L8ht6ML7RQl2nRBVLlTlVmmxqlZwmomnhQ+meM9TkYORREI4AmfM5V1 CUMMwpg8BB7WA5SYhvgtdd4mZIw3uVrY66Xh1gIOq+zrIOxMDwzvva0pHoWYiuPn oiwyTZEzTYPdn4p3yum2O4EvASuj7g== =hB4N -----END PGP SIGNATURE----- --XWOWbaMNXpFDWE00--