From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sanford Rockowitz Subject: I2C failures with recent laptops and docking stations Date: Sat, 6 May 2017 03:31:31 -0400 Message-ID: <590D7BD3.2050108@minsoft.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1728180923==" Return-path: Received: from fallback-in2.mxes.net (fallback-out2.mxes.net [216.86.168.191]) by gabe.freedesktop.org (Postfix) with ESMTPS id 313DD6E27B for ; Sat, 6 May 2017 07:38:53 +0000 (UTC) Received: from mxout-08.mxes.net (mxout-08.mxes.net [216.86.168.183]) by fallback-in2.mxes.net (Postfix) with ESMTP id 2ECB02FD7AF for ; Sat, 6 May 2017 03:31:34 -0400 (EDT) List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org This is a multi-part message in MIME format. --===============1728180923== Content-Type: multipart/alternative; boundary="------------030906000703080009000509" This is a multi-part message in MIME format. --------------030906000703080009000509 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable The following bug was just posted: i915 failures with recent chips and docking stations and follows up this thread in= the intel-gfx mailing list. Per suggestion of Jani Nikula of Intel, I'm also posting a brief summary to this list. I am the developer of ddcutil , a Linux utility that manages monitor settings using DDC/CI. I am seeing a pattern of user error reports in which I2C communication is not working when a system with a recent Intel chip, using the i915 driver, is plugged into a docking station. ddcutil looks for displays by examining all non-SMBus /dev/i2c devices on the system. If checks for the presence of slave address x50 and x37. If they exist it tries to read the EDID on x50 and a Virtual Control Panel feature value on x37. Examining one of the user logs, I see that two /dev/i2c-n devices have udev sysattr name DPMST. When ddcutil probes those /dev/i2c devices, slave addresses x50 and x37 appear active, but reading the EDID fails. Per Jani Nikola, this is likely a bug in the core drm DP MST code. Sanford Rockowitz --------------030906000703080009000509 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit The following bug was just posted: i915 failures with recent chips and docking stations and follows up this thread in the intel-gfx mailing list.  Per suggestion of Jani Nikula of Intel, I'm also posting a brief summary to this list.

I am the developer of ddcutil, a Linux utility that manages monitor settings using DDC/CI. I am seeing a pattern of user error reports in which I2C communication is not working when a system with a recent Intel chip, using the i915 driver, is plugged into a docking station.

ddcutil looks for displays by examining all non-SMBus /dev/i2c devices on the system. If checks for the presence of slave address x50 and x37. If they exist it tries to read the EDID on x50 and a Virtual Control Panel feature value on x37. Examining one of the user logs, I see that two  /dev/i2c-n devices have udev sysattr name DPMST. When ddcutil probes those /dev/i2c devices, slave addresses x50 and x37 appear active, but reading the EDID fails.

Per Jani Nikola, this is likely a bug in the core drm DP MST code.

Sanford Rockowitz



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