[PATCH] input: ti_am335x_tsc: Add open delay parameter

[Michael Welling]

Adds a device tree parameter to set the open delay on the touchscreen
conversion steps. Increasing this parameter helps the touch accuracy on
some screens.

Signed-off-by: Michael Welling <mwelling@xxxxxxxx>
---
 .../bindings/input/touchscreen/ti-tsc-adc.txt          |  5 +++++
 drivers/input/touchscreen/ti_am335x_tsc.c              | 18 ++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
index b1163bf..cb11fda 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
@@ -41,6 +41,11 @@ Optional properties:
 			 charge step, so this does in fact function as a
 			 hardware knob for adjusting the amount of "settling
 			 time".
+	ti,open-delay: Open delay applied to all touchscreen conversion steps.
+			The value corresponds to the number of ADC clock
+			cycles to wait after applying the step configuration
+			registers and before sending the start of ADC
+			conversion. Maximum value is 0x3FFFF.
 
 - child "adc"
 	ti,chan-step-opendelay: List of open delays for each channel of
diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index 191a1b8..37a9729 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -54,6 +54,7 @@ struct titsc {
 	u32			inp_xp, inp_xn, inp_yp, inp_yn;
 	u32			step_mask;
 	u32			charge_delay;
+	u32			open_delay;
 };
 
 static unsigned int titsc_readl(struct titsc *ts, unsigned int reg)
@@ -148,7 +149,7 @@ 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), ts_dev->open_delay);
 	}
 
 	config = 0;
@@ -172,7 +173,7 @@ 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), ts_dev->open_delay);
 	}
 
 	/* Make CHARGECONFIG same as IDLECONFIG */
@@ -188,13 +189,13 @@ 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);
+			ts_dev->open_delay);
 
 	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);
+			ts_dev->open_delay);
 
 	/* The steps end ... end - readouts * 2 + 2 and bit 0 for TS_Charge */
 	stepenable = 1;
@@ -392,6 +393,15 @@ static int titsc_parse_dt(struct platform_device *pdev,
 		dev_warn(&pdev->dev, "ti,charge-delay not specified\n");
 	}
 
+	err = of_property_read_u32(node, "ti,open-delay",
+				   &ts_dev->open_delay);
+	/*
+	 * If ti,open-delay value is not specified, then use
+	 * STEPCONFIG_OPENDLY as the default value.
+	 */
+	if (err < 0)
+		ts_dev->open_delay = STEPCONFIG_OPENDLY;
+
 	return of_property_read_u32_array(node, "ti,wire-config",
 			ts_dev->config_inp, ARRAY_SIZE(ts_dev->config_inp));
 }
-- 
2.1.4

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