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: Sat, 17 Oct 2015 19:57:26 +0200 Message-ID: <20151017175726.GB3359@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="LpQ9ahxlCli8rRTG" Return-path: Received: from sauhun.de ([89.238.76.85]:50610 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751652AbbJQR5c (ORCPT ); Sat, 17 Oct 2015 13:57:32 -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 --LpQ9ahxlCli8rRTG 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 Applied to for-current with Pavel's Tested-by:, thanks! --LpQ9ahxlCli8rRTG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWIowGAAoJEBQN5MwUoCm2HtUP/Aym2c6U7R9xGPmR/XsPDGMN Db2v0R5FdV1nn+NiB4njIbaJFrAZ0ZMenQo/Ln/E3MPK/0PorJ5fP5KHMzu0VZvs CwmfJvS/6oO5qAKsOinwOl9xmS63gfH3JCvJ8MoYJ9Ln1oDeNSCZ54RQRQBK3BLm ICWuCs40+cZMngOODlUEW08IaoJAbaoS2/gtmv0slRn6O84moCTGuN0vXTDo7rW1 8Vi30KDHbwwx4u6GXowGhzvnx5dIde3xUgCQ41H/wE27rLNX5fmg7Is7SxlZ1ubR VjJKc86I7eEGezPXZbirw/tvwE9czl7RwGdGkUMhU4aF4a3hrhnYtqZPdOJdOoFG 8L06n3MO7m9kz0F8OSie33AdsE2W2U6IQsNUO2db5Xxp1kLReotVjHPSkBH9TBus dXN9s8h1bymzcGrRmBLJ/uwKg71q0PPGG5iWU00aCqR0MoSBKqmdyj9guadaUlHE T4MYi7h1i/hWLddRxhIRJvofXExNLjwRM3XBiyBh3TQDVSaN3RHO3mMRd4dfiUsv RcamrlMQ5XCX9IS4Da6wd5guR2lJpHTXMiBoIfRltVMp52NVrnQpR/f6mwDcf0fi mTfj3KG9Iqfr+fs+aL5SmmGlQ63KbJcJTHc0GnOj2F/FmrlGZyONfC/f2e0pR/cH PBFwogsBfghHrciahK68 =p+ou -----END PGP SIGNATURE----- --LpQ9ahxlCli8rRTG--