[PATCH 0/4] Touchscreen performance related fixes

Richard Cochran richardcochran at gmail.com
Mon Nov 3 10:09:21 PST 2014

On Mon, Oct 27, 2014 at 04:38:27PM +0530, Vignesh R wrote:
> This series of patches fix TSC defects related to lag in touchscreen
> performance and cursor jump at touch release. The lag was result of
> udelay in TSC interrupt handler. Cursor jump due to false pen-up event.
> The patches implement Advisory 1.0.31 in silicon errata of am335x-evm
> to avoid false pen-up events and remove udelay.

That advisory has two workarounds. You have chosen the second one?

The text of the second workaround says it only works on 4 wire setups,
so I wonder how 5 wire designs will be affected.

> The advisory says to use
> steps 1 to 4 for ADC and 5 to 16 for TSC (assuming 4 wire TSC and 4 channel
> ADC).

No, it doesn't say that. (sprz360f.pdf)

> Further the X co-ordinate must be the last one to be sampled just
> before charge step. The first two patches implement the required changes. 

FWIW, I implemented the first workaround and removed the udelay not
too long ago. Like Sebastian, I saw the TSC unit hang after about
50000 interrupts when running with the workaround.

Did you test you patch for very long?


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