On Wed, Mar 6, 2013 at 3:35 AM, Benson Leung <bleung at chromium.org> wrote: > 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. Can you please retest with latest drm-intel-fixes merged into -rc1? Paulo's patch fixes a race in handling PCH interrupts (where the gmbus hw is) which matches rather well with your description here. Thanks, Daniel > commit 2c438c0273b76d6cb158f8bdd0aa3ebf66e48a28 > Author: Daniel Vetter <daniel.vetter at ffwll.ch> > 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 <imre.deak at intel.com> > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> > > > Is there anything I can do to help debug this some more? > > -- > Benson Leung > Software Engineer, Chrom* OS > bleung at chromium.org -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
