The i.MX6UL internal touchscreen controller contains an option to
average upon samples. This feature reduces noise from the produced
touch locations.
This patch adds sample averaging support to the imx6ul_tsc device
driver.
Signed-off-by: Guy Shapiro <guy.shapiro@xxxxxxxxxxxxx>
---
drivers/input/touchscreen/imx6ul_tsc.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/input/touchscreen/imx6ul_tsc.c b/drivers/input/touchscreen/imx6ul_tsc.c
index 8275267..31724d9 100644
--- a/drivers/input/touchscreen/imx6ul_tsc.c
+++ b/drivers/input/touchscreen/imx6ul_tsc.c
@@ -25,6 +25,7 @@
/* ADC configuration registers field define */
#define ADC_AIEN (0x1 << 7)
#define ADC_CONV_DISABLE 0x1F
+#define ADC_AVGE (0x1 << 5)
#define ADC_CAL (0x1 << 7)
#define ADC_CALF 0x2
#define ADC_12BIT_MODE (0x2 << 2)
@@ -32,6 +33,7 @@
#define ADC_CLK_DIV_8 (0x03 << 5)
#define ADC_SHORT_SAMPLE_MODE (0x0 << 4)
#define ADC_HARDWARE_TRIGGER (0x1 << 13)
+#define ADC_AVGS_SHIFT 14
#define SELECT_CHANNEL_4 0x04
#define SELECT_CHANNEL_1 0x01
#define DISABLE_CONVERSION_INT (0x0 << 7)
@@ -86,6 +88,7 @@ struct imx6ul_tsc {
int measure_delay_time;
int pre_charge_time;
+ int average_samples;
struct completion completion;
};
@@ -107,6 +110,8 @@ static int imx6ul_adc_init(struct imx6ul_tsc *tsc)
adc_cfg = readl(tsc->adc_regs + REG_ADC_CFG);
adc_cfg |= ADC_12BIT_MODE | ADC_IPG_CLK;
adc_cfg |= ADC_CLK_DIV_8 | ADC_SHORT_SAMPLE_MODE;
+ if (tsc->average_samples)
+ adc_cfg |= (tsc->average_samples - 1) << ADC_AVGS_SHIFT;
adc_cfg &= ~ADC_HARDWARE_TRIGGER;
writel(adc_cfg, tsc->adc_regs + REG_ADC_CFG);
@@ -118,6 +123,8 @@ static int imx6ul_adc_init(struct imx6ul_tsc *tsc)
/* start ADC calibration */
adc_gc = readl(tsc->adc_regs + REG_ADC_GC);
adc_gc |= ADC_CAL;
+ if (tsc->average_samples)
+ adc_gc |= ADC_AVGE;
writel(adc_gc, tsc->adc_regs + REG_ADC_GC);
timeout = wait_for_completion_timeout
@@ -450,6 +457,16 @@ static int imx6ul_tsc_probe(struct platform_device *pdev)
if (err)
tsc->pre_charge_time = 0xfff;
+ err = of_property_read_u32(np, "average-samples",
+ &tsc->average_samples);
+ if (err)
+ tsc->average_samples = 0;
+ if (tsc->average_samples > 4) {
+ dev_err(&pdev->dev, "average-samples (%u) must be [0-4]\n",
+ tsc->average_samples);
+ return -EINVAL;
+ }
+
err = input_register_device(tsc->input);
if (err) {
dev_err(&pdev->dev,
--
2.1.4
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