[PATCH] Enable ADC Filter on UCB1400

[Marek Vasut <marek.vasut@gmail.com>]

Hi!

please consider applying the following patch. I tested it on Palm Tungsten|C 
(ADCSYNC connected, both disabled and enabled through module parameter) and a 
friend of mine tested it on Toradex Colibri (ADCSYNC not connected, disabled).

Thanks

>From 65cb92df1aba511fbc44d62fa25d5cf38a687952 Mon Sep 17 00:00:00 2001
From: Marek Vasut <marek.vasut@gmail.com>
Date: Thu, 30 Jul 2009 19:03:10 +0200
Subject: [PATCH] Enable ADC Filter on UCB1400

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>
---
 drivers/input/touchscreen/ucb1400_ts.c |    6 ++++++
 include/linux/ucb1400.h                |    4 ++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/input/touchscreen/ucb1400_ts.c 
b/drivers/input/touchscreen/ucb1400_ts.c
index b2828a3..df8e5f3 100644
--- a/drivers/input/touchscreen/ucb1400_ts.c
+++ b/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 +383,11 @@ 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);
diff --git a/include/linux/ucb1400.h b/include/linux/ucb1400.h
index 464fb34..e489ff6 100644
--- a/include/linux/ucb1400.h
+++ b/include/linux/ucb1400.h
@@ -74,6 +74,10 @@
 
 #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
-- 
1.6.3.3