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

From: [email-masked] (Richard Cochran)
Date: Mon, 17 Nov 2014 09:23:37 +0100

On Mon, Nov 17, 2014 at 09:57:05AM +0530, Vignesh R wrote:
> My patches are based on v3.18rc2. I tested my patches on am335x-evm
> using tslib.

No beaglebone + cape testing?

> Please explain "touch is broken"? What is the behaviour of TSC?

With plain v3.17 plus your series, the cursor is almost never near the
pen. Mostly it jitters around the right hand edge.

My customer had already changed the step delay (I think by trial and
error, not sure) in order to get the cursor near the pen. I ported
this change onto your series (see patch, below), but still the pen up
event causes a huge cursor jump.

(Again, I did solve the pen up issue, but in a totally different
way. I never posted the fix, because I could not be sure that it would
work on a wide variety of boards.)

> Which ADC channels are being used for TSC?

&tscadc {
	status = "okay";
	tsc {
		ti,wires = <4>;
		ti,x-plate-resistance = <300>;
		ti,coordinate-readouts = <5>;
		ti,wire-config = <0x00 0x11 0x23 0x32>;
	};

	adc {
		ti,adc-channels = <5 6 7>;
	};
};

So for this particular design, your series really does not help, not
even a little. You did not test the series on many boards. I am
concerned that this series only works on the one board you did test,
and that it may break functionality on other people's boards.

Thanks,
Richard

---
diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index b84493f..77a4883 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -148,7 +148,7 @@ static void titsc_step_config(struct titsc *ts_dev)
 	end_step = first_step + tsc_steps;
 	for (i = end_step - ts_dev->coordinate_readouts; i < end_step; i++) {
 		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
-		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
+		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY | STEPDELAY_SAMPLE(20));
 	}
 
 	config = 0;
@@ -172,7 +172,7 @@ static void titsc_step_config(struct titsc *ts_dev)
 	end_step = first_step + ts_dev->coordinate_readouts;
 	for (i = first_step; i < end_step; i++) {
 		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
-		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
+		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY | STEPDELAY_SAMPLE(20));
 	}
 
 	/* Make CHARGECONFIG same as IDLECONFIG */
@@ -188,13 +188,13 @@ static void titsc_step_config(struct titsc *ts_dev)
 			STEPCONFIG_INP(ts_dev->inp_xp);
 	titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
 	titsc_writel(ts_dev, REG_STEPDELAY(end_step),
-			STEPCONFIG_OPENDLY);
+			STEPCONFIG_OPENDLY | STEPDELAY_SAMPLE(20));
 
 	end_step++;
 	config |= STEPCONFIG_INP(ts_dev->inp_yn);
 	titsc_writel(ts_dev, REG_STEPCONFIG(end_step), config);
 	titsc_writel(ts_dev, REG_STEPDELAY(end_step),
-			STEPCONFIG_OPENDLY);
+			STEPCONFIG_OPENDLY | STEPDELAY_SAMPLE(20));
 
 	/* The steps end ... end - readouts * 2 + 2 and bit 0 for TS_Charge */
 	stepenable = 1;