Re: [PATCH v4 2/6] input: touchscreen: ti_am335x_tsc: Remove udelay in interrupt handler

On Sunday 16 November 2014 12:57 AM, Richard Cochran wrote:

On Fri, Nov 14, 2014 at 10:37:27AM +0530, Vignesh R wrote:

quoted

From: Brad Griffis <redacted>

TSC interrupt handler had udelay to avoid reporting of false pen-up
interrupt to user space. This patch implements workaround suggesting in
Advisory 1.0.31 of silicon errata for am335x, thus eliminating udelay
and touchscreen lag. This also improves performance of touchscreen and
eliminates sudden jump of cursor at touch release.

I back ported this series onto v3.15.1 in order to try this out on a
custom, beaglebone-like board. With this series, the touch is really
broken. (I had fixed the pen up problem in a totally different way for
a customer, and so I wanted to try out your solution.)

I will try to port the board code to a more recent kernel to try your
series again. With which kernel version did you test your patches?

And which board?

Thanks for testing these patches.

My patches are based on v3.18rc2. I tested my patches on am335x-evm
using tslib.
If you are encountering false pen-ups, charge-delay parameter needs to
be tuned to your board. In some custom setups charge-delay of 0xB000
provided better performance.
If you are using ts_test (from tslib) for testing try
# ts_test > /dev/null
for better performance.

Please explain "touch is broken"? What is the behaviour of TSC?
Which ADC channels are being used for TSC?

Regards
Vignesh

Thanks,
Richard