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 16:02:37 +0100 Message-ID: <20151130150236.GL1513@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="2EnvhqpWJq810sZn" Return-path: Received: from sauhun.de ([89.238.76.85]:33234 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754135AbbK3PCm (ORCPT ); Mon, 30 Nov 2015 10:02:42 -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 --2EnvhqpWJq810sZn 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 and added stable, thanks! --2EnvhqpWJq810sZn Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWXGUMAAoJEBQN5MwUoCm2b5cP/3llZ1XddAG7S/56WqnFwIcs 74cfYtCZOLJABBVLPMIBS4L42BEe/Qh5mdG/LNv8rYbKeI0axRYDrVXzfonsRzf6 TebO5+zCbX4tJ4u2+Arc6nk+ao9NgqE3zHcLP+aBjIpMckI8DQ6+Iyd+t3FMRxc3 99Pp8+PyGLwxc8qapuqGHRDBADDb1GVasVDpwRAA1yljvoxMn0rtwRw62JcyhVzQ cAIUUcM41fpnupQp3vstlTWkiGEgdLXBiI6QJ+oRjSYNSs/idmO2dkZwLpku45yW AMJoDHadeK8MaZFns637J+0zXltDzX5DGRCMISt5Es73E6g1b6Zw0Ag/T8FYalSQ sIQA9OJyrclsoHvPicziixX7GrLJiryzCLCJWuNiyGPElBQuwTbeQI3PPKCvEV6l haIN6WfCULpx/9nyEP/gEecFnxGn4LTV6Yg5frmNDoHmqXC9gZyAj5G2OAWCSeo/ pCJOZEMRKj5rPjPXXsVB79lNxzOX4PwhgTnlmM0n/eMJGOS59b7ZFkqlODlKQB1o ipxgX5ecciOIb4zp/NrHnwmpBG0YtEivqT6E4OMM9DMc7mQbIFuRWQWZvmFnfL8Q Z6FXlwRHLum/2NtPVMW/SaqCgdvjeDQSEsOeC4zey5MGnNt0Mfu0V8VeGLqvFi2m a8pBiOezvuPdBXVaeUsz =5pEU -----END PGP SIGNATURE----- --2EnvhqpWJq810sZn--