--- /dev/null
+From abe8f448547d1bd69ac2963e07e2657f27b79691 Mon Sep 17 00:00:00 2001
+From: I-Fan Chen <tick@openmoko.com>
+Date: Wed, 29 Oct 2008 03:15:18 +0000
+Subject: [PATCH] palliate_touch_screen_jitter.patch
+
+ S3C24XX touchscreen: To palliate the data jitter from touchpanel
+ Thanks to Dima Kogan patch eff39cde0d3cdd2afd5e1b4be5a8eb6cf195543e,
+ in which try to balence the up/down events, and inspired this patch.
+ We can observe a serious up/down jitter phenomenon when touching the touchscreen lightly.
+ This only happens when the press pressure is pretty light:
+ eg. large scale light touch,
+ starting to touch,
+ or going to move finger from touch panel.
+ This will make user space library think it got extra click events.
+ In order to palliate with this phenomenon, we delayed the up event for a while,
+ and see if it is a jitter or not.
+ The threshold is crucial. If it is too long, multiple clicks will be filtered out.
+ If it is too short we did not filter anything out.
+ From the log and some survey we can see that the interval of two clicks is generally over 0.1 sec.
+ And Most jitter events happens in 0.3 sec.
+ And the longest duration of vision is about 1/16 sec, and it's not easy for human to notice.
+ So I choose 1/16 sec as the threshold.
+ This filters out most (not all) jitter events, and preserves the normal behavior we expected.
+
+Signed-off-by: I-Fan Chen <tick@openmoko.com>
+---
+ drivers/input/touchscreen/s3c2410_ts.c | 47 +++++++++++++++++---------------
+ 1 files changed, 25 insertions(+), 22 deletions(-)
+
+diff --git a/drivers/input/touchscreen/s3c2410_ts.c b/drivers/input/touchscreen/s3c2410_ts.c
+index fc1c500..95672ff 100644
+--- a/drivers/input/touchscreen/s3c2410_ts.c
++++ b/drivers/input/touchscreen/s3c2410_ts.c
+@@ -78,6 +78,12 @@
+
+ #define DEBUG_LVL KERN_DEBUG
+
++#define TOUCH_STANDBY_FLAG 0
++#define TOUCH_PRESSED_FLAG 1
++#define TOUCH_RELEASE_FLAG 2
++
++#define TOUCH_RELEASE_TIMEOUT (HZ >> 4)
++
+ MODULE_AUTHOR("Arnaud Patard <arnaud.patard@rtp-net.org>");
+ MODULE_DESCRIPTION("s3c2410 touchscreen driver");
+ MODULE_LICENSE("GPL");
+@@ -131,7 +137,7 @@ static void clear_raw_fifo(void)
+ ts.raw_running_avg.x = 0;
+ ts.raw_running_avg.y = 0;
+ ts.flag_previous_exceeded_threshold = 0;
+- ts.flag_first_touch_sent = 0;
++ ts.flag_first_touch_sent = TOUCH_STANDBY_FLAG;
+ }
+
+
+@@ -143,6 +149,10 @@ static inline void s3c2410_ts_connect(void)
+ s3c2410_gpio_cfgpin(S3C2410_GPG15, S3C2410_GPG15_nYPON);
+ }
+
++static void touch_timer_fire(unsigned long data);
++static struct timer_list touch_timer =
++ TIMER_INITIALIZER(touch_timer_fire, 0, 0);
++
+ static void touch_timer_fire(unsigned long data)
+ {
+ unsigned long data0;
+@@ -155,18 +165,9 @@ static void touch_timer_fire(unsigned long data)
+ updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) &&
+ (!(data1 & S3C2410_ADCDAT0_UPDOWN));
+
+- // if we need to send an untouch event, but we haven't yet sent the
+- // touch event (this happens if the touchscreen was tapped lightly),
+- // send the touch event first
+- if (!updown && !ts.flag_first_touch_sent && ts.count != 0) {
+- input_report_abs(ts.dev, ABS_X, ts.xp >> ts.shift);
+- input_report_abs(ts.dev, ABS_Y, ts.yp >> ts.shift);
+-
+- input_report_key(ts.dev, BTN_TOUCH, 1);
+- input_report_abs(ts.dev, ABS_PRESSURE, 1);
+- input_sync(ts.dev);
+- ts.flag_first_touch_sent = 1;
+- }
++ if ( updown && ts.flag_first_touch_sent == TOUCH_RELEASE_FLAG ) {
++ ts.flag_first_touch_sent = TOUCH_PRESSED_FLAG;
++ }
+
+ if (updown) {
+ if (ts.count != 0) {
+@@ -189,7 +190,7 @@ static void touch_timer_fire(unsigned long data)
+ input_report_key(ts.dev, BTN_TOUCH, 1);
+ input_report_abs(ts.dev, ABS_PRESSURE, 1);
+ input_sync(ts.dev);
+- ts.flag_first_touch_sent = 1;
++ ts.flag_first_touch_sent = TOUCH_PRESSED_FLAG;
+ }
+
+ ts.xp = 0;
+@@ -202,19 +203,21 @@ static void touch_timer_fire(unsigned long data)
+ S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
+ } else {
+ ts.count = 0;
+-
+- input_report_key(ts.dev, BTN_TOUCH, 0);
+- input_report_abs(ts.dev, ABS_PRESSURE, 0);
+- input_sync(ts.dev);
+- ts.flag_first_touch_sent = 0;
++
++ if ( ts.flag_first_touch_sent == TOUCH_RELEASE_FLAG ) {
++ input_report_key(ts.dev, BTN_TOUCH, 0);
++ input_report_abs(ts.dev, ABS_PRESSURE, 0);
++ input_sync(ts.dev);
++ ts.flag_first_touch_sent = TOUCH_STANDBY_FLAG;
++ } if ( ts.flag_first_touch_sent == TOUCH_PRESSED_FLAG ) {
++ ts.flag_first_touch_sent = TOUCH_RELEASE_FLAG;
++ mod_timer(&touch_timer, jiffies + TOUCH_RELEASE_TIMEOUT);
++ }
+
+ writel(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
+ }
+ }
+
+-static struct timer_list touch_timer =
+- TIMER_INITIALIZER(touch_timer_fire, 0, 0);
+-
+ static irqreturn_t stylus_updown(int irq, void *dev_id)
+ {
+ unsigned long data0;
+--
+1.5.6.5
+
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