Openmoko Bug #2328: touschreen sometimes stops generating events

[Openmoko Public Trac]

#2328: touschreen sometimes stops generating events
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 Reporter:  lindi   |          Owner:  openmoko-kernel
     Type:  defect  |         Status:  new            
 Priority:  normal  |      Milestone:                 
Component:  kernel  |        Version:                 
 Severity:  normal  |       Keywords:  touchscreen    
 Haspatch:  0       |      Blockedby:                 
Estimated:          |    Patchreview:                 
 Blocking:          |   Reproducible:  rarely         
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Comment(by gena2x):

 issue is caused by thing i called 'unexpected interrupts'. then device is
 touched up/down interrupt recieved, but original drivers do not rely on
 interrupt cause, they check adc registers for current state instead. this
 may cause that 'down' interrupt recieved while handler thinks this is
 'up', that leads to situation then driver no longer watch for down
 interrupts and ts generate no events until ts driver reload. other
 situation then 'up' interrupt is interpreted as 'down' sometimes lead to
 data corruption is adc conversion and 'number remaining of samples need'
 can go below 0, so adc conversion will be requested for infinite amount of
 times. in this case attempt to reloading module will hang system. as
 driver written with some 'states' in mind it can't handle such interrupts
 and in fact they are not interesting for us (is we already have pen down,
 no need for more interrupt informing as about this), so we have to ignore
 em.

 for me some thing left unexplained - sometimes recieving interrupts while
 we totally not expect them, and why we see this problem only on kernel
 without debugging information.

 mine solution for this is to accept only expected interrupts.

 some logs of failures with added debug info:
 http://www.bsdmn.com/openmoko/kernel/touchscreen/34failexpectupgotdown.log
 http://www.bsdmn.com/openmoko/kernel/touchscreen/34failexpectdowngotup.log
 http://www.bsdmn.com/openmoko/kernel/touchscreen/34unknowunexpected.log

 patches for .34 and .29 kernel:
 http://www.bsdmn.com/openmoko/kernel/touchscreen/touchscreen_ignoreunexpectedintr29.patch
 http://www.bsdmn.com/openmoko/kernel/touchscreen/touchscreen_ignoreunexpectedintr34.patch

 .34 patch were tested much more than .29 version for which only basic test
 very done.

 i hope this bug fix is good step forward to kernel optimized for speed.

-- 
Ticket URL: <https://docs.openmoko.org/trac/ticket/2328#comment:6>
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