From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH v2] i2c: davinci: Increase module clock frequency Date: Mon, 30 Nov 2015 15:56:04 +0100 Message-ID: <20151130145604.GK1513@katana> References: <564DBEE3.4030508@nokia.com> <20151130135504.GE1513@katana> <565C566C.7000809@nokia.com> <20151130141054.GG1513@katana> <565C6254.6080602@nokia.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="qDymnuGqqhW10CwH" Return-path: Received: from sauhun.de ([89.238.76.85]:33192 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754071AbbK3O4I (ORCPT ); Mon, 30 Nov 2015 09:56:08 -0500 Content-Disposition: inline In-Reply-To: <565C6254.6080602@nokia.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Alexander Sverdlin Cc: Sekhar Nori , Kevin Hilman , linux-i2c@vger.kernel.org, Murali Karicheri , Santosh Shilimkar --qDymnuGqqhW10CwH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 30, 2015 at 03:51:00PM +0100, Alexander Sverdlin wrote: > I2C controller used in Keystone SoC has an undocumented peculiarity which > results in SDA-SCL margins being dependent on module clock. Driving high > capacity bus near its limits can result in STOP condition sometimes being > understood as REPEATED-START by slaves (or NACK instead of ACK, etc...). > Driving the module with higher clocks increases the margin between SDA an= d SCL > transitions, making the operations with higher bus rates more robust. The= refore, > target the module clock to 12MHz instead of 7MHz, still staying within > the specification limits. >=20 > Before the change STOP timing looked like this on 400kHz: >=20 Applied to for-current, thanks! --qDymnuGqqhW10CwH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWXGOEAAoJEBQN5MwUoCm2r74P/1OuYz/KQaiHJPPuu0NrSXym pBJV0FJeLFa8tQN4Gi2R0cccA9rDMw3hXqWvA7/MvzJYg0VS1eak25xCRhQei0KK sVkQkhoy4dXrADdpwshLSEd0vAL/xzVWTzVyipKe5GpRgiJQoqmRecoCmZaLbyRv 7JbK4us9PDP4lJ7iAX/7GJ+9WDbOUxlimkxs4JObIGCtkw+fbDH744fsG0kv/YMb /+IDwhGuvOvZCqkU7MuircA+e894uMO38QkD0Hfev0BHnQXT6yhMl9Sakqq8f0/N e0OY2J0LBlQlRXei5kUYjmSnJiZSnaRYIpykQkDPUE8J0i69iNeLt4LoYOtVQriO 3Awv0qeA/pgsVN6ZO5hOJgOuosGiOIKFvGWUlcHOBgGmbIey75PwlAaZBieSv+Tb MWcVSseexlmy/B8YtVyl5bkfhAdj9VHu//xcY2n0NxdYRFCyLL1DU0ymCVB2VU0I cjAYmGbxlMatc387n6pE81rOLSXXtyPIjBzyC4RECF/3xrtn/HovgdDvrRlwXl4c j7SDidEM0Js2zizBfzXNU6F3viF2u8WKrmvq1vX+1s3kMKOD8xOwu8zZGDuW+tgR Ts9UgTu2NtlTOjPaqG6fs5vbOsnFmFx38Xp/6rA79XU3dzzwBxdM6QFRN6ArHKag 9v2ogBei1Anc/AeDxNjb =EfRI -----END PGP SIGNATURE----- --qDymnuGqqhW10CwH--