From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH] i2c: designware: Do not use parameters from ACPI on Dell Inspiron 7348 Date: Thu, 15 Oct 2015 13:40:29 +0200 Message-ID: <20151015114029.GB1546@katana> References: <1443085614-101362-1-git-send-email-mika.westerberg@linux.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="WYTEVAkct0FjGQmd" Return-path: Received: from sauhun.de ([89.238.76.85]:38155 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752600AbbJOLkg (ORCPT ); Thu, 15 Oct 2015 07:40:36 -0400 Content-Disposition: inline In-Reply-To: <1443085614-101362-1-git-send-email-mika.westerberg@linux.intel.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Mika Westerberg Cc: Christian Ruppert , Jarkko Nikula , Pavel Roskin , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org --WYTEVAkct0FjGQmd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Sep 24, 2015 at 12:06:54PM +0300, Mika Westerberg wrote: > ACPI SSCN/FMCN methods were originally added because then the platform can > provide the most accurate HCNT/LCNT values to the driver. However, this > seems not to be true for Dell Inspiron 7348 where using these causes the > touchpad to fail in boot: >=20 > i2c_hid i2c-DLL0675:00: failed to retrieve report from device. > i2c_designware INT3433:00: i2c_dw_handle_tx_abort: lost arbitration > i2c_hid i2c-DLL0675:00: failed to retrieve report from device. > i2c_designware INT3433:00: controller timed out >=20 > The values received from ACPI are (in fast mode): >=20 > HCNT: 72 > LCNT: 160 >=20 > this translates to following timings (input clock is 100MHz on Broadwell): >=20 > tHIGH: 720 ns (spec min 600 ns) > tLOW: 1600 ns (spec min 1300 ns) > Bus period: 2920 ns (assuming 300 ns tf and tr) > Bus speed: 342.5 kHz >=20 > Both tHIGH and tLOW are within the I2C specification. >=20 > The calculated values when ACPI parameters are not used are (in fast mode= ): >=20 > HCNT: 87 > LCNT: 159 >=20 > which translates to: >=20 > tHIGH: 870 ns (spec min 600 ns) > tLOW: 1590 ns (spec min 1300 ns) > Bus period 3060 ns (assuming 300 ns tf and tr) > Bus speed 326.8 kHz >=20 > These values are also within the I2C specification. >=20 > Since both ACPI and calculated values meet the I2C specification timing > requirements it is hard to say why the touchpad does not function properly > with the ACPI values except that the bus speed is higher in this case (but > still well below the max 400kHz). >=20 > Solve this by adding DMI quirk to the driver that disables using ACPI > parameters on this particulare machine. >=20 > Reported-by: Pavel Roskin > Signed-off-by: Mika Westerberg Pavel, have you tested this patch? --WYTEVAkct0FjGQmd Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWH5CtAAoJEBQN5MwUoCm2wS4P/10psTf9cfhS4z6iI3HLQ72x E4tLWvWNlRt/sijg73U3K+T4j7qYiJnTNkpUogwch3Me2etP6e5qkzOvv0xX+pxH wR9aplNs0NmSPu23kJTD02kkTP4I9EhDqv4XWhtZQ8zBjRAvgW8A2oPBnv9pr+0A 4Z/DQTXgzwCDbOnfNSg1Wcs3schCHfWPGDqZCJS2D2S3KohbpYeJc0ZMpixJUlGg /3HacoA3zAPhZ5TTOc8qdjAmfZ01zgkaOdittJgKZ//Ox2sbFcPzqY+pJ+f6yrQh DJ/aNBp7PR8VOspPLHGThBISyHRN4V3qAaRePqo+7WRK47x5iFgofnZYDn9bAR6P RDN+T7Ce8fgM+P92eaDI18RgDYS1Klp5NDYb7FI/9JlLfGgX/o1I5kBIqOHrBlUN EVTISEks+tI5t9CcUZcd4XFZsLgWWAvlb7AID8k7HvJae40FmHfo9c1Fmp0DAgu/ vd1QYSaN/5qkYaEXGN/8dhkOb1sN3aJ1+gYJrrARboFoIV/DLYYKzRTqzufxNWfT pHfImPimeOdczSisiJaBq5HDa8hJZ6EfCBgyH2iZFAhKQWJGoKQFjIaOdtmyNo77 OJY++b/fAnHMqiwBjvL/6mzBcLwU2BfxLtt7BTH4wv5oqF5qWL8NsoYLI9Cm+4qS gdpanfz0LO/BnoZbd4wI =wAX2 -----END PGP SIGNATURE----- --WYTEVAkct0FjGQmd--