[v4,2/6] input: touchscreen: ti_am335x_tsc: Remove udelay in interrupt handler
diff mbox

Message ID 1415941651-28962-3-git-send-email-vigneshr@ti.com
State New, archived
Headers show

Commit Message

Vignesh Raghavendra Nov. 14, 2014, 5:07 a.m. UTC
From: Brad Griffis <bgriffis@ti.com>

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.

IDLECONFIG and CHARGECONFIG registers are to be configured
with same values in order to eliminate false pen-up events. This
workaround may result in false pen-down to be detected, hence considerable
charge step delay needs to be added. The charge delay is set to 0xB000
(in terms of ADC clock cycles) by default.

TSC steps are disabled at the end of every sampling cycle and EOS bit is
set. Once the EOS bit is set, the TSC steps need to be re-enabled to begin
next sampling cycle.

Signed-off-by: Brad Griffis <bgriffis@ti.com>
[vigneshr@ti.com: Ported the patch from v3.12 to v3.18rc2]

Signed-off-by: Vignesh R <vigneshr@ti.com>
---

v4:
 - check for PEN_IRQ bit in ADCFSM to avoid false-pen when ADC
   and TSC are used together.
 - Set charge delay to 0x400 as default. Most devices function
   normally at this value.

 drivers/input/touchscreen/ti_am335x_tsc.c | 63 ++++++++++++++-----------------
 include/linux/mfd/ti_am335x_tscadc.h      |  3 +-
 2 files changed, 30 insertions(+), 36 deletions(-)

Comments

Richard Cochran Nov. 15, 2014, 7:27 p.m. UTC | #1
On Fri, Nov 14, 2014 at 10:37:27AM +0530, Vignesh R wrote:
> From: Brad Griffis <bgriffis@ti.com>
> 
> 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,
Richard


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Vignesh Raghavendra Nov. 17, 2014, 4:27 a.m. UTC | #2
On Sunday 16 November 2014 12:57 AM, Richard Cochran wrote:
> On Fri, Nov 14, 2014 at 10:37:27AM +0530, Vignesh R wrote:
>> From: Brad Griffis <bgriffis@ti.com>
>>
>> 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
> 
> 
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Patch
diff mbox

diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index 1aeac9675fe7..b94719fc8849 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -173,11 +173,9 @@  static void titsc_step_config(struct titsc *ts_dev)
 		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
 	}
 
-	/* Charge step configuration */
-	config = ts_dev->bit_xp | ts_dev->bit_yn |
-			STEPCHARGE_RFP_XPUL | STEPCHARGE_RFM_XNUR |
-			STEPCHARGE_INM_AN1 | STEPCHARGE_INP(ts_dev->inp_yp);
+	/* Make CHARGECONFIG same as IDLECONFIG */
 
+	config = titsc_readl(ts_dev, REG_IDLECONFIG);
 	titsc_writel(ts_dev, REG_CHARGECONFIG, config);
 	titsc_writel(ts_dev, REG_CHARGEDELAY, CHARGEDLY_OPENDLY);
 
@@ -261,12 +259,34 @@  static irqreturn_t titsc_irq(int irq, void *dev)
 {
 	struct titsc *ts_dev = dev;
 	struct input_dev *input_dev = ts_dev->input;
-	unsigned int status, irqclr = 0;
+	unsigned int fsm, status, irqclr = 0;
 	unsigned int x = 0, y = 0;
 	unsigned int z1, z2, z;
-	unsigned int fsm;
 
-	status = titsc_readl(ts_dev, REG_IRQSTATUS);
+	status = titsc_readl(ts_dev, REG_RAWIRQSTATUS);
+	if (status & IRQENB_HW_PEN) {
+		ts_dev->pen_down = true;
+		titsc_writel(ts_dev, REG_IRQWAKEUP, 0x00);
+		titsc_writel(ts_dev, REG_IRQCLR, IRQENB_HW_PEN);
+		irqclr |= IRQENB_HW_PEN;
+	}
+
+	if (status & IRQENB_PENUP) {
+		fsm = titsc_readl(ts_dev, REG_ADCFSM);
+		if (fsm == ADCFSM_STEPID) {
+			ts_dev->pen_down = false;
+			input_report_key(input_dev, BTN_TOUCH, 0);
+			input_report_abs(input_dev, ABS_PRESSURE, 0);
+			input_sync(input_dev);
+		} else {
+			ts_dev->pen_down = true;
+		}
+		irqclr |= IRQENB_PENUP;
+	}
+
+	if (status & IRQENB_EOS)
+		irqclr |= IRQENB_EOS;
+
 	/*
 	 * ADC and touchscreen share the IRQ line.
 	 * FIFO1 interrupts are used by ADC. Handle FIFO0 IRQs here only
@@ -297,34 +317,6 @@  static irqreturn_t titsc_irq(int irq, void *dev)
 		}
 		irqclr |= IRQENB_FIFO0THRES;
 	}
-
-	/*
-	 * Time for sequencer to settle, to read
-	 * correct state of the sequencer.
-	 */
-	udelay(SEQ_SETTLE);
-
-	status = titsc_readl(ts_dev, REG_RAWIRQSTATUS);
-	if (status & IRQENB_PENUP) {
-		/* Pen up event */
-		fsm = titsc_readl(ts_dev, REG_ADCFSM);
-		if (fsm == ADCFSM_STEPID) {
-			ts_dev->pen_down = false;
-			input_report_key(input_dev, BTN_TOUCH, 0);
-			input_report_abs(input_dev, ABS_PRESSURE, 0);
-			input_sync(input_dev);
-		} else {
-			ts_dev->pen_down = true;
-		}
-		irqclr |= IRQENB_PENUP;
-	}
-
-	if (status & IRQENB_HW_PEN) {
-
-		titsc_writel(ts_dev, REG_IRQWAKEUP, 0x00);
-		titsc_writel(ts_dev, REG_IRQCLR, IRQENB_HW_PEN);
-	}
-
 	if (irqclr) {
 		titsc_writel(ts_dev, REG_IRQSTATUS, irqclr);
 		am335x_tsc_se_set_cache(ts_dev->mfd_tscadc, ts_dev->step_mask);
@@ -417,6 +409,7 @@  static int titsc_probe(struct platform_device *pdev)
 	}
 
 	titsc_writel(ts_dev, REG_IRQENABLE, IRQENB_FIFO0THRES);
+	titsc_writel(ts_dev, REG_IRQENABLE, IRQENB_EOS);
 	err = titsc_config_wires(ts_dev);
 	if (err) {
 		dev_err(&pdev->dev, "wrong i/p wire configuration\n");
diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
index e2e70053470e..3f4e994ace2b 100644
--- a/include/linux/mfd/ti_am335x_tscadc.h
+++ b/include/linux/mfd/ti_am335x_tscadc.h
@@ -52,6 +52,7 @@ 
 
 /* IRQ enable */
 #define IRQENB_HW_PEN		BIT(0)
+#define IRQENB_EOS		BIT(1)
 #define IRQENB_FIFO0THRES	BIT(2)
 #define IRQENB_FIFO0OVRRUN	BIT(3)
 #define IRQENB_FIFO0UNDRFLW	BIT(4)
@@ -107,7 +108,7 @@ 
 /* Charge delay */
 #define CHARGEDLY_OPEN_MASK	(0x3FFFF << 0)
 #define CHARGEDLY_OPEN(val)	((val) << 0)
-#define CHARGEDLY_OPENDLY	CHARGEDLY_OPEN(1)
+#define CHARGEDLY_OPENDLY	CHARGEDLY_OPEN(0x400)
 
 /* Control register */
 #define CNTRLREG_TSCSSENB	BIT(0)