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Subject[PATCH v6 4/6] input: touchscreen: ti_am335x_tsc: Read charge delay from DT
Date
This patch reads charge delay from tsc DT node and writes to
REG_CHARGEDELAY register. If the charge delay is not specified in DT
then default value of 0x400(CHARGEDLY_OPENDLY) is used.

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

v6:
- Move Documentation from DT patch to driver code.

v5:
- print out a warning when ti,charge-delay is not specified

v4:
- Set charge delay to 0x400 as default. Most devices function normally
at this value

.../devicetree/bindings/input/touchscreen/ti-tsc-adc.txt | 15 +++++++++++++++
drivers/input/touchscreen/ti_am335x_tsc.c | 14 +++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
index 878549ba814d..6c4fb34823d3 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
+++ b/Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
@@ -28,6 +28,20 @@ Required properties:
ti,adc-channels: List of analog inputs available for ADC.
AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.

+Optional properties:
+- child "tsc"
+ ti,charge-delay: Length of touch screen charge delay step in terms of
+ ADC clock cycles. Charge delay value should be large
+ in order to avoid false pen-up events. This value
+ effects the overall sampling speed, hence need to be
+ kept as low as possible, while avoiding false pen-up
+ event. Start from a lower value, say 0x400, and
+ increase value until false pen-up events are avoided.
+ The pen-up detection happens immediately after the
+ charge step, so this does in fact function as a
+ hardware knob for adjusting the amount of "settling
+ time".
+
Example:
tscadc: tscadc@44e0d000 {
compatible = "ti,am3359-tscadc";
@@ -36,6 +50,7 @@ Example:
ti,x-plate-resistance = <200>;
ti,coordiante-readouts = <5>;
ti,wire-config = <0x00 0x11 0x22 0x33>;
+ ti,charge-delay = <0x400>;
};

adc {
diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index 0625c102a1d0..7c0f6b21559d 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -52,6 +52,7 @@ struct titsc {
u32 bit_xp, bit_xn, bit_yp, bit_yn;
u32 inp_xp, inp_xn, inp_yp, inp_yn;
u32 step_mask;
+ u32 charge_delay;
};

static unsigned int titsc_readl(struct titsc *ts, unsigned int reg)
@@ -177,7 +178,7 @@ static void titsc_step_config(struct titsc *ts_dev)

config = titsc_readl(ts_dev, REG_IDLECONFIG);
titsc_writel(ts_dev, REG_CHARGECONFIG, config);
- titsc_writel(ts_dev, REG_CHARGEDELAY, CHARGEDLY_OPENDLY);
+ titsc_writel(ts_dev, REG_CHARGEDELAY, ts_dev->charge_delay);

/* coordinate_readouts + 1 ... coordinate_readouts + 2 is for Z */
config = STEPCONFIG_MODE_HWSYNC |
@@ -368,6 +369,17 @@ static int titsc_parse_dt(struct platform_device *pdev,
if (err < 0)
return err;

+ err = of_property_read_u32(node, "ti,charge-delay",
+ &ts_dev->charge_delay);
+ /*
+ * If ti,charge-delay value is not specified, then use
+ * CHARGEDLY_OPENDLY as the default value.
+ */
+ if (err < 0) {
+ ts_dev->charge_delay = CHARGEDLY_OPENDLY;
+ dev_warn(&pdev->dev, "ti,charge-delay not specified\n");
+ }
+
return of_property_read_u32_array(node, "ti,wire-config",
ts_dev->config_inp, ARRAY_SIZE(ts_dev->config_inp));
}
--
1.9.1


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