Re: AM335x touchscreen issues

[Michael Welling <mwelling-EkmVulN54Sk@public.gmane.org>]

On Tue, May 26, 2015 at 09:15:53PM +0000, Cooper Jr., Franklin wrote:
> Michael,
> 
> Can you send me the output of ts_test_raw after you done a 5 or so touch down and touch up events? In the output let me know at which point in the log that the issue you observed has occurred. Please try to avoid moving your finger since I want to see the full output of that program but I'm not interested any unnecessary pen down events.
>

Oddly the repeated pen up and down events do not occur when running ts_print_raw:
root@som3517-som200:~# ts_print_raw 
1418169393.147827:   1648   2075    206
1418169393.229976:   1725   1983    240
1418169393.312154:   1731   1980    240
1418169393.394333:   1706   2043    239
1418169393.476523:   1703   2028    241
1418169393.558708:   1714   2041    240
1418169393.640888:   1704   2041    240
1418169393.721556:      0      0      0
1418169395.283096:   2889   2512    192
1418169395.365236:   2947   2486    210
1418169395.447413:   2949   2470    211
1418169395.529606:   2943   2497    211
1418169395.611759:   2922   2506    211
1418169395.693935:   2866   2474    213
1418169395.776135:   2858   2481    214
1418169395.858305:   2861   2451    213
1418169395.938972:      0      0      0
1418169397.482867:   1083   1981    236
1418169397.565026:   1157   1832    254
1418169397.647217:   1161   1856    256
1418169397.729412:   1158   1883    255
1418169397.811583:   1159   1841    255
1418169397.893760:   1159   1864    256
1418169397.975947:   1158   1893    256
1418169398.056605:      0      0      0
1418169399.690290:   2299   2372    178
1418169399.772432:   2388   2160    221
1418169399.854611:   2391   2190    223
1418169399.936802:   2379   2207    223
1418169400.018966:   2389   2184    223
1418169400.101146:   2383   2208    224
1418169400.183338:   2381   2203    223
1418169400.264012:      0      0      0
1418169402.073266:   1230   2381    212
1418169402.155413:   1301   2097    247
1418169402.237590:   1313   2077    248
1418169402.319772:   1307   2126    248
1418169402.401948:   1304   2096    248
1418169402.484127:   4078   2155     58
1418169402.564801:      0      0      0

Here is what the output of ts_test looks like without even touching the screen:
root@som3517-som200:~# ts_test               
1418169549.722957:    816     17     58
1418169549.803604:    816     17      0
1418169549.817757:    816     25     58
1418169549.898411:    816     25      0
1418169549.912828:    816     41     59
1418169549.993463:    816     41      0
1418169550.007771:    816     28     58
1418169550.088404:    816     28      0
1418169550.102828:    816     33     58
1418169550.183486:    816     33      0
1418169550.197767:    816     42     59
1418169550.278401:    816     42      0
1418169550.292970:    816     23     58
1418169550.373604:    816     23      0
1418169550.387773:    816     28     58
1418169550.468404:    816     28      0
1418169550.482955:    816     32     59
1418169550.563600:    816     32      0
1418169550.577773:    816     25     58
1418169550.658406:    816     25      0
1418169550.672827:    816     35     59
1418169550.753464:    816     35      0
1418169550.767761:    816     42     59
1418169550.848407:    816     42      0
1418169550.862826:    816     41     59
1418169550.943462:    816     41      0
1418169550.958013:    816     37     59
1418169551.038655:    816     37      0
1418169551.052824:    816     41     59
1418169551.133475:    816     41      0
1418169551.147774:    816     28     58
1418169551.228406:    816     28      0
.
.

> I recently encountered several touchscreen problems that I am working on submitting to mainline. Below are the variety of issues I discovered and fixed but its currently based on 3.14 kernel.
> 
> 1. The x and y location right before a penup event is usually incorrect. Visibly the causes the cursor to jump right before a touchup. So I implemented a way to ignore that incorrect event.
> 2. I discovered that for some reason a series of touch up events are sent back to back. So I added something to ignore consecutive pen up events.
> 3. Sometimes a pen down event is reported with a pressure of 0. I noticed applications like ts_lib looked at the pressure and thought a pressure of 0 means a finger was lifted. So I added a patch that ignored 0 pressure pen down events. This prevented premature touchups.
> 4. I added debouncing. Essentially the driver didn't report any touch events for a user specified number of ms after a pen up occured. It was noticed especially during touchscreen calibration that after a person lifted their finger after touching the screen a combination of pen up and pen down events were incorrectly detected.
> 
> Most likely a combination of 2-4 is your problem. I think the udelay acted like an unintentional debounce which is probably why it wasn't discovered sooner.
> > >
> > > --
> > > balbi
> > 
>