Input: ucb1400_ts - enable ADC Filter

This patch enables ADC filtering on UCB1400 codec by default. The
benefit from this change is mostly on some Colibri boards where
the ADCSYNC pin of the UCB1400 codec isn't connected causing the
touchscreen to jitter very badly. This change has no visible
effect on boards where the ADCSYNC pin is connected.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Tested-by: Palo Revak <palo@bielyvlk.sk>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/touchscreen/ucb1400_ts.c

@@ -345,6 +345,7 @@ static int ucb1400_ts_detect_irq(struct ucb1400_ts *ucb)
 static int ucb1400_ts_probe(struct platform_device *dev)
 {
 	int error, x_res, y_res;
+	u16 fcsr;
 	struct ucb1400_ts *ucb = dev->dev.platform_data;
 
 	ucb->ts_idev = input_allocate_device();
@@ -382,6 +383,14 @@ static int ucb1400_ts_probe(struct platform_device *dev)
 	ucb->ts_idev->evbit[0]		= BIT_MASK(EV_ABS) | BIT_MASK(EV_KEY);
 	ucb->ts_idev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
 
+	/*
+	 * Enable ADC filter to prevent horrible jitter on Colibri.
+	 * This also further reduces jitter on boards where ADCSYNC
+	 * pin is connected.
+	 */
+	fcsr = ucb1400_reg_read(ucb->ac97, UCB_FCSR);
+	ucb1400_reg_write(ucb->ac97, UCB_FCSR, fcsr | UCB_FCSR_AVE);
+
 	ucb1400_adc_enable(ucb->ac97);
 	x_res = ucb1400_ts_read_xres(ucb);
 	y_res = ucb1400_ts_read_yres(ucb);

include/linux/ucb1400.h

@@ -73,6 +73,10 @@
 
 #define UCB_ADC_DATA		0x68
 #define UCB_ADC_DAT_VALID	(1 << 15)
+
+#define UCB_FCSR		0x6c
+#define UCB_FCSR_AVE		(1 << 12)
+
 #define UCB_ADC_DAT_MASK	0x3ff
 
 #define UCB_ID			0x7e