Re: AM335x touchscreen issues

[Michael Welling <mwelling@ieee.org>]

On Tue, May 26, 2015 at 09:34:10PM +0000, Cooper Jr., Franklin wrote:
> 
> 
> > -----Original Message-----
> > From: Michael Welling [mailto:mwelling79@gmail.com] On Behalf Of Michael
> > Welling
> > Sent: Tuesday, May 26, 2015 4:29 PM
> > To: Cooper Jr., Franklin
> > Cc: Balbi, Felipe; dmitry.torokhov@gmail.com; R, Vignesh; Griffis, Brad;
> > jic23@kernel.org; wsa@the-dreams.de; linux-input@vger.kernel.org;
> > GWilson@sakuraus.com; linux-iio@vger.kernel.org
> > Subject: Re: AM335x touchscreen issues
> > 
> > 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
> [Franklin] So your saying the above ts_test is being ran and you never touched the screen?
Yes.

> Looking at the mailing list post you sent earlier it seems like the goal is for the ADC to be used at the same time. 
> Is that the case when you ran both ts_test and ts_print_raw?

No. I am not sampling the ADC. 

This happening without any interaction with the screen.

> 
> 
> > .
> > .
> > 
> > > 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
> > > >
> > >