Input: ads7846 - improve filtering for thumb press accuracy
Providing more accurate coordinates for thumb press requires additional
steps in the filtering logic:
- Ignore samples found invalid by the debouncing logic, or the ones that
have out of bound pressure value.
- Add a parameter to repeat debouncing, so that more then two consecutive
good readings are required for a valid sample.
Signed-off-by: Imre Deak <imre.deak@nokia.com>
Acked-by: Juha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 1aaa153..1494175 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -71,6 +71,7 @@
__be16 x;
__be16 y;
__be16 z1, z2;
+ int ignore;
};
struct ads7846 {
@@ -81,6 +82,7 @@
u16 model;
u16 vref_delay_usecs;
u16 x_plate_ohms;
+ u16 pressure_max;
u8 read_x, read_y, read_z1, read_z2, pwrdown;
u16 dummy; /* for the pwrdown read */
@@ -88,12 +90,15 @@
struct spi_transfer xfer[10];
struct spi_message msg[5];
+ struct spi_message *last_msg;
int msg_idx;
int read_cnt;
+ int read_rep;
int last_read;
u16 debounce_max;
u16 debounce_tol;
+ u16 debounce_rep;
spinlock_t lock;
struct timer_list timer; /* P: lock */
@@ -354,6 +359,14 @@
} else
Rt = 0;
+ /* Sample found inconsistent by debouncing or pressure is beyond
+ * the maximum. Don't report it to user space, repeat at least
+ * once more the measurement */
+ if (ts->tc.ignore || Rt > ts->pressure_max) {
+ mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
+ return;
+ }
+
/* NOTE: "pendown" is inferred from pressure; we don't rely on
* being able to check nPENIRQ status, or "friendly" trigger modes
* (both-edges is much better than just-falling or low-level).
@@ -402,25 +415,45 @@
struct ads7846 *ts = ads;
struct spi_message *m;
struct spi_transfer *t;
- u16 val;
+ int val;
int status;
m = &ts->msg[ts->msg_idx];
t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
val = (*(u16 *)t->rx_buf) >> 3;
-
- if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol
- && ts->read_cnt < ts->debounce_max)) {
- /* Repeat it, if this was the first read or the read wasn't
- * consistent enough
- */
- ts->read_cnt++;
- ts->last_read = val;
+ if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol)) {
+ /* Repeat it, if this was the first read or the read
+ * wasn't consistent enough. */
+ if (ts->read_cnt < ts->debounce_max) {
+ ts->last_read = val;
+ ts->read_cnt++;
+ } else {
+ /* Maximum number of debouncing reached and still
+ * not enough number of consistent readings. Abort
+ * the whole sample, repeat it in the next sampling
+ * period.
+ */
+ ts->tc.ignore = 1;
+ ts->read_cnt = 0;
+ /* Last message will contain ads7846_rx() as the
+ * completion function.
+ */
+ m = ts->last_msg;
+ }
+ /* Start over collecting consistent readings. */
+ ts->read_rep = 0;
} else {
- /* Go for the next read */
- ts->msg_idx++;
- ts->read_cnt = 0;
- m++;
+ if (++ts->read_rep > ts->debounce_rep) {
+ /* Got a good reading for this coordinate,
+ * go for the next one. */
+ ts->tc.ignore = 0;
+ ts->msg_idx++;
+ ts->read_cnt = 0;
+ ts->read_rep = 0;
+ m++;
+ } else
+ /* Read more values that are consistent. */
+ ts->read_cnt++;
}
status = spi_async(ts->spi, m);
if (status)
@@ -609,8 +642,15 @@
ts->model = pdata->model ? : 7846;
ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
- ts->debounce_max = pdata->debounce_max ? : 1;
- ts->debounce_tol = pdata->debounce_tol ? : 10;
+ ts->pressure_max = pdata->pressure_max ? : ~0;
+ if (pdata->debounce_max) {
+ ts->debounce_max = pdata->debounce_max;
+ ts->debounce_tol = pdata->debounce_tol;
+ ts->debounce_rep = pdata->debounce_rep;
+ if (ts->debounce_rep > ts->debounce_max + 1)
+ ts->debounce_rep = ts->debounce_max - 1;
+ } else
+ ts->debounce_tol = ~0;
ts->get_pendown_state = pdata->get_pendown_state;
snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
@@ -728,6 +768,8 @@
m->complete = ads7846_rx;
m->context = ts;
+ ts->last_msg = m;
+
if (request_irq(spi->irq, ads7846_irq,
SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
spi->dev.bus_id, ts)) {
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index d8823e2..adb3dafd 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -15,9 +15,11 @@
u16 y_min, y_max;
u16 pressure_min, pressure_max;
- u16 debounce_max; /* max number of readings per sample */
+ u16 debounce_max; /* max number of additional readings
+ * per sample */
u16 debounce_tol; /* tolerance used for filtering */
-
+ u16 debounce_rep; /* additional consecutive good readings
+ * required after the first two */
int (*get_pendown_state)(void);
};