#10417 NORM Future : Enable Synaptics mode for CL1A/CL1B/CL1C touchpad

Zarro Boogs per Child bugtracker at laptop.org
Wed Oct 5 12:11:50 EDT 2011

#10417: Enable Synaptics mode for CL1A/CL1B/CL1C touchpad
           Reporter:  martin.langhoff  |       Owner:  cjb           
               Type:  enhancement      |      Status:  new           
           Priority:  normal           |   Milestone:  Future Release
          Component:  distro           |     Version:  not specified 
         Resolution:                   |    Keywords:                
        Next_action:  never set        |    Verified:  0             
Deployment_affected:                   |   Blockedby:                
           Blocking:                   |  

Comment(by rsmith):

 Replying to [comment:20 dsd]:

 > However, I still think this EC issue is worth looking into if you can
 spare the time. Running the device at half rate in absolute mode causes
 6*40=240 bytes of incoming data per second, which is exactly the same as
 if we run at full rate in relative mode (3*80=240), and is less data than
 we will now receive for AVC pads (4*80=320). So if 240bytes/sec from the
 mouse can starve the keyboard, then it is possible that we may also have
 problems in our other configurations. (btw, i have confirmed that running
 absolute mode at half rate has the same keyboard-starving effect that you
 saw with full rate)

 In abosolute mode the problem isn't really so much the absolute rate as
 much is the constant stream of data.  You can't go faster than the EC will
 process the data because the PS/2 lines are flow controlled.  Full rate
 would be 480 bytes per second which is a byte ever 2ms.  The handlers for
 the transition from PS/2 bus to LPC bus in the EC are main loop driven (ie
 not in interrupt context) and the loop time is > 2ms. (I've not measured
 it recently but I know its > 2ms)  So there's no point in operating at
 full rate. At 4ms/byte of half rate it might keep up but I'll have to

 The keyboard and and touchpad data both have to go upstream via the same
 data register for the LPC bus. With PS2 data essentially always available
 in this case the keyboard data isn't getting a chance to get processed.  I
 tried a few trivial things to try and help this but it appears to be more
 complex than that.

 Relative mode may be the short term win in the mean time because the data
 stream will have gaps that allow for keys to make it up the chain.

Ticket URL: <http://dev.laptop.org/ticket/10417#comment:21>
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