From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH] i2c: sirf: tune the divider to make i2c bus freq more accurate Date: Fri, 23 Oct 2015 22:30:52 +0200 Message-ID: <20151023203052.GI1520@katana> References: <1441794632-4074-1-git-send-email-21cnbao@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="WR+jf/RUebEcofwt" Return-path: Received: from sauhun.de ([89.238.76.85]:36802 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256AbbJWUaz (ORCPT ); Fri, 23 Oct 2015 16:30:55 -0400 Content-Disposition: inline In-Reply-To: <1441794632-4074-1-git-send-email-21cnbao@gmail.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Barry Song <21cnbao@gmail.com> Cc: linux-i2c@vger.kernel.org, workgroup.linux@csr.com, Guoying Zhang , Barry Song --WR+jf/RUebEcofwt Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Sep 09, 2015 at 10:30:32AM +0000, Barry Song wrote: > From: Guoying Zhang >=20 > In prima2 and atlas7, due to some hardware design issue. we > need to adjust the divider ratio a little according to i2c > bus frequency ranges. > Since i2c is open drain interface that allows the slave to > stall the transaction by holding the SCL line at '0', the RTL > implementation is waiting for SCL feedback from the pin after > setting it to High-Z ('1'). This wait adds to the high-time > interval counter few cycles of the input synchronization > (depending on the SCL_FILTER_REG field), and also the time it > takes for the board pull-up resistor to rise the SCL line. > For slow SCL settings these additions are negligible, but they > start to affect the speed when clock is set to faster frequencies. > This patch is based on the actual tests, and it makes SCL more > accurate. >=20 > Signed-off-by: Guoying Zhang > Signed-off-by: Barry Song Applied to for-next, thanks! --WR+jf/RUebEcofwt Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWKpj7AAoJEBQN5MwUoCm2CCIQAJCwevqUxCn2KCyy9MNh3zSQ 4jHgJVd2DWaQQiUKcgXVcNqUQCgUhCpPKbq1i40uDFqsHID2x4ee/GqGBe92t8zA hG0N+QU7U6LpPRdt69PbWf0es8i3WavbF7Y7w7BB9/Zw9s3h/7kdhUjIH6F93BrI E8YprCum6m79e8f1IsmsrEIBvxGb4FSoZfYrkvRQ6uUre3uuDvQv5ucA/F2tA3GO dPTmIG/bELVSeRJ9IlsC4bEU1sP2fURV13ENGr+faOy2AJ/2q+jkL0aUrGoylbpH 8OXQMj1jI2oosperdR2onCORzFtLCZJAJJ5XmpfLJs89oy2MM7bg+u93kpvHGvSY xvRdS1Nt4Np62EjQNBn2AkR+sEWM0DFkunBcCkFAZnEXYFgrGfqqwN6l0ZjeuyFu 473iR69/0UcNBtCE02pnLZ3HiMxjcBlPS4+rjC3Z2+7te3Njvaikj0RcdjUbz0L6 0kFcJWj6/q9N89zudal6/N3MMqVsQ29S4Vbc4h2N2yuoSqlYa9XoSi8k/cSZZJDG EnvD9v7ZlkmhyXV2SdDv0EL53YftvfCO6GhtYPzPCTus4HFFf9ig37zEva97Y/TZ JzLjRAxkPxN57eS7Tk9NumqUyCfrx9i+IhvoRIunAt8xh4rV0rr36uvjhT2+D2pb DgDsUZbrRrRX32y9Yv9Z =PwbR -----END PGP SIGNATURE----- --WR+jf/RUebEcofwt--