Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753331Ab3CFCfL (ORCPT ); Tue, 5 Mar 2013 21:35:11 -0500 Received: from mail-ob0-f174.google.com ([209.85.214.174]:52645 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858Ab3CFCfH (ORCPT ); Tue, 5 Mar 2013 21:35:07 -0500 MIME-Version: 1.0 Date: Tue, 5 Mar 2013 18:35:07 -0800 X-Google-Sender-Auth: 7CaswUGBkRk0R8O0QGKdwaVuNRw Message-ID: Subject: v3.9-rc1 instability on Chromebook Pixel with gmbus irq From: Benson Leung To: daniel.vetter@ffwll.ch Cc: Daniel Kurtz , Yufeng Shen , Olof Johansson , dri-devel@lists.freedesktop.org, "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2384 Lines: 58 Hi Daniel Vetter, I'm working on touch devices Chromium OS, and I've noticed a regression between 3.8 and 3.9-rc1, which was posted yesterday. The hardware in question is a Chromebook Pixel. For this device, we have i2c input devices: atmel mxt224s touchpad and atmel mxt1664s touchscreen. The touchpad is on bus 1, "i915 gmbus vga" at 1-004b. The touchscreen is on bus 2, "i915 gmbus panel" at 2-004a. I was testing v3.9-rc1 on the Pixel and the touchscreen driver is being returned -110 (-ETIMEDOUT) on an i2c_transfer after several seconds of both touch devices working correctly. At the time of the failure, there are no error messages from GMBUS that I can see, but the bus never recovers. I can keep interacting with the touchscreen or touchpad, and the interrupts trigger reads, but all subsequent reads return -110. I noticed that between 3.8 and 3.9-rc1, your patch series to add gmbus irq support was merged. After bisecting, I found that this commit seems to be causing the timeout problem. Reverting it makes the problem go away, and the bus is stable. commit 2c438c0273b76d6cb158f8bdd0aa3ebf66e48a28 Author: Daniel Vetter Date: Sat Dec 1 13:53:46 2012 +0100 drm/i915: use gmbus irq to wait for gmbus idle GMBUS_ACTIVE has inverted sense and so doesn't fit into the wait_hw_status helper, hence create a new gmbus_wait_idle functions. Also, we only care about the idle irq event and nothing else, which allows us to use the wait_event_timeout helper directly without jumping through hoops to catch NAKs. Since gen2/3 don't have gmbus interrupts, handle them separately with the old wait_for macro. This shaves another few ms off reading EDID from a hdmi screen on my testbox here. EDID reading with interrupt driven gmbus is now as fast as with busy-looping gmbus at 28 ms here (with negligible cpu overhead). Reviewed-by: Imre Deak Signed-off-by: Daniel Vetter Is there anything I can do to help debug this some more? -- Benson Leung Software Engineer, Chrom* OS bleung@chromium.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/