From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH v2 14/16] mfd: intel-lpss: Pass SDA hold time to I2C host controller driver Date: Mon, 8 Feb 2016 11:09:43 +0100 Message-ID: <20160208100942.GA2220@tetsubishi> References: <1448896304-87928-1-git-send-email-andriy.shevchenko@linux.intel.com> <1448896304-87928-15-git-send-email-andriy.shevchenko@linux.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="VbJkn9YxBvnuCH5J" Return-path: Content-Disposition: inline In-Reply-To: <1448896304-87928-15-git-send-email-andriy.shevchenko@linux.intel.com> Sender: linux-acpi-owner@vger.kernel.org To: Andy Shevchenko Cc: "Rafael J . Wysocki" , Greg Kroah-Hartman , Jarkko Nikula , linux-i2c@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Lee Jones , Mika Westerberg , Kevin Fenzi , Arnd Bergmann List-Id: linux-i2c@vger.kernel.org --VbJkn9YxBvnuCH5J Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 30, 2015 at 05:11:42PM +0200, Andy Shevchenko wrote: > From: Mika Westerberg >=20 > Intel Skylake the LPSS I2C pad circuit has internal delays that require > programming non-zero SDA hold time for the I2C host controller. If this is > not done communication to slave devices may fail with arbitration lost > errors like the one seen below taken from Lenovo Yoga 900: >=20 > i2c_hid i2c-SYNA2B29:00: Fetching the HID descriptor > i2c_hid i2c-SYNA2B29:00: __i2c_hid_command: cmd=3D20 00 > i2c_designware i2c_designware.1: i2c_dw_handle_tx_abort: lost arbitrati= on >=20 > To fix this we follow what the Windows driver is doing and pass the defau= lt > SDA hold time of 230 ns to all Intel Skylake host controllers. This still > allows the platform to override these values by passing special ACPI > methods SSCN and FMCN. >=20 > Reported-by: Kevin Fenzi > Signed-off-by: Mika Westerberg > Signed-off-by: Andy Shevchenko There has been a request to get this into stable: https://bugzilla.kernel.org/show_bug.cgi?id=3D108581 Since we probably don't want to backport the whole device_property series, is there a simpler fix to backport for stable? --VbJkn9YxBvnuCH5J Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWuGlmAAoJEBQN5MwUoCm2RhEQAKpEZorTihLh528lRO4tR2MQ rexKAfITZ3MdAFRKcvPlslnYeWAu2v3BYZ3h9Mbm3h9W4AtMCm6aLtEQ0KL83RnK ikpAhALQm206O8D988SKD6m3nmmqq2ynd376ZPi3O4IJGKG3Q5HfY4sfpWZtg4rQ UbTZWpegL7vqAjFLVQg1uHCvtSgfR2jwE/b2PsYKfM8Q55mQeGs5Tc7BECUiTJMW UZkUcIDi26ATByabwnidpxdPl3vp+h+uaTcVHuF91w+uhNmZjJhSbeqloBDxN5Ir 5lXM6kt6KVXaLMFnNaJpysAkPM076l+uoe/CVtGVxmSYkvO53H51aVHj34XXM3MC SX1gU9zJFzSYejy9JbzNtqvWC+u9ncujTxmqR/N8xjoS6nHLiK17DEJC3uigXGDa y67tQgr2u25XtoUTTib0/9JfzwwCFrDrueI8MWQ9Kw/QVNBLYfcoze6gtocP42rj MizbGaudyNQgMOgvCzXenikc9eZkIKYgQtfCpZyi2ldzIX9RyYaV0Ddz3vE7R5sP x3n/hkmLESyd5YfNLmIXQOVdnfM/aokePukuj8lfppMBIECsg7EQ3CXN9p6Lt/8t ENvgsit6y2Z/wx+UGWZ/0vkSt5icIpH7fhaYBayM765Lz+oxnHbeMltaew8xsbjb V+bnWDhJ4VXucN+O6tCB =sa2K -----END PGP SIGNATURE----- --VbJkn9YxBvnuCH5J--