Input: ads7846 - pluggable filtering logic

Some LCDs like the LS041Y3 require a customized filtering
logic for reliable readings, so make the filtering function
replacable through platform specific hooks.

Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 105 insertions, 40 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index c6164b6f476a..03e527c16c23 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -63,11 +63,11 @@ struct ts_event {
         /* For portability, we can't read 12 bit values using SPI (which
          * would make the controller deliver them as native byteorder u16
          * with msbs zeroed).  Instead, we read them as two 8-bit values,
-         * which need byteswapping then range adjustment.
+         * *** WHICH NEED BYTESWAPPING *** and range adjustment.
          */
-        __be16 x;
-        __be16 y;
-        __be16 z1, z2;
+        u16     x;
+        u16     y;
+        u16     z1, z2;
         int    ignore;
 };
 
@@ -106,6 +106,9 @@ struct ads7846 {
         unsigned                irq_disabled:1; /* P: lock */
         unsigned                disabled:1;
 
+        int                     (*filter)(void *data, int data_idx, int *val);
+        void                    *filter_data;
+        void                    (*filter_cleanup)(void *data);
         int                     (*get_pendown_state)(void);
 };
 
@@ -379,13 +382,13 @@ static void ads7846_rx(void *ads)
         u16                     x, y, z1, z2;
         unsigned long           flags;
 
-        /* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
-         * built from two 8 bit values written msb-first.
+        /* ads7846_rx_val() did in-place conversion (including byteswap) from
+         * on-the-wire format as part of debouncing to get stable readings.
          */
-        x = (be16_to_cpu(ts->tc.x) >> 3) & 0x0fff;
-        y = (be16_to_cpu(ts->tc.y) >> 3) & 0x0fff;
-        z1 = (be16_to_cpu(ts->tc.z1) >> 3) & 0x0fff;
-        z2 = (be16_to_cpu(ts->tc.z2) >> 3) & 0x0fff;
+        x = ts->tc.x;
+        y = ts->tc.y;
+        z1 = ts->tc.z1;
+        z2 = ts->tc.z2;
 
         /* range filtering */
         if (x == MAX_12BIT)
@@ -453,50 +456,85 @@ static void ads7846_rx(void *ads)
         spin_unlock_irqrestore(&ts->lock, flags);
 }
 
-static void ads7846_debounce(void *ads)
+static int ads7846_debounce(void *ads, int data_idx, int *val)
 {
         struct ads7846          *ts = ads;
-        struct spi_message      *m;
-        struct spi_transfer     *t;
-        int                     val;
-        int                     status;
 
-        m = &ts->msg[ts->msg_idx];
-        t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
-        val = (be16_to_cpu(*(__be16 *)t->rx_buf) >> 3) & 0x0fff;
-        if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol)) {
+        if (!ts->read_cnt || (abs(ts->last_read - *val) > ts->debounce_tol)) {
+                /* Start over collecting consistent readings. */
+                ts->read_rep = 0;
                 /* 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->last_read = *val;
                         ts->read_cnt++;
+                        return ADS7846_FILTER_REPEAT;
                 } 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;
+                        return ADS7846_FILTER_IGNORE;
                 }
-                /* Start over collecting consistent readings. */
-                ts->read_rep = 0;
         } else {
                 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
+                        return ADS7846_FILTER_OK;
+                } else {
                         /* Read more values that are consistent. */
                         ts->read_cnt++;
+                        return ADS7846_FILTER_REPEAT;
+                }
+        }
+}
+
+static int ads7846_no_filter(void *ads, int data_idx, int *val)
+{
+        return ADS7846_FILTER_OK;
+}
+
+static void ads7846_rx_val(void *ads)
+{
+        struct ads7846 *ts = ads;
+        struct spi_message *m;
+        struct spi_transfer *t;
+        u16 *rx_val;
+        int val;
+        int action;
+        int status;
+
+        m = &ts->msg[ts->msg_idx];
+        t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
+        rx_val = t->rx_buf;
+
+        /* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
+         * built from two 8 bit values written msb-first.
+         */
+        val = be16_to_cpu(*rx_val) >> 3;
+
+        action = ts->filter(ts->filter_data, ts->msg_idx, &val);
+        switch (action) {
+        case ADS7846_FILTER_REPEAT:
+                break;
+        case ADS7846_FILTER_IGNORE:
+                ts->tc.ignore = 1;
+                /* Last message will contain ads7846_rx() as the
+                 * completion function.
+                 */
+                m = ts->last_msg;
+                break;
+        case ADS7846_FILTER_OK:
+                *rx_val = val;
+                ts->tc.ignore = 0;
+                m = &ts->msg[++ts->msg_idx];
+                break;
+        default:
+                BUG();
         }
         status = spi_async(ts->spi, m);
         if (status)
@@ -689,14 +727,25 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
         ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
         ts->pressure_max = pdata->pressure_max ? : ~0;
-        if (pdata->debounce_max) {
+
+        if (pdata->filter != NULL) {
+                if (pdata->filter_init != NULL) {
+                        err = pdata->filter_init(pdata, &ts->filter_data);
+                        if (err < 0)
+                                goto err_free_mem;
+                }
+                ts->filter = pdata->filter;
+                ts->filter_cleanup = pdata->filter_cleanup;
+        } else if (pdata->debounce_max) {
                 ts->debounce_max = pdata->debounce_max;
+                if (ts->debounce_max < 2)
+                        ts->debounce_max = 2;
                 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;
+                ts->filter = ads7846_debounce;
+                ts->filter_data = ts;
         } else
-                ts->debounce_tol = ~0;
+                ts->filter = ads7846_no_filter;
         ts->get_pendown_state = pdata->get_pendown_state;
 
         snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
@@ -737,7 +786,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         x->len = 2;
         spi_message_add_tail(x, m);
 
-        m->complete = ads7846_debounce;
+        m->complete = ads7846_rx_val;
         m->context = ts;
 
         m++;
@@ -755,7 +804,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         x->len = 2;
         spi_message_add_tail(x, m);
 
-        m->complete = ads7846_debounce;
+        m->complete = ads7846_rx_val;
         m->context = ts;
 
         /* turn y+ off, x- on; we'll use formula #2 */
@@ -774,7 +823,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                 x->len = 2;
                 spi_message_add_tail(x, m);
 
-                m->complete = ads7846_debounce;
+                m->complete = ads7846_rx_val;
                 m->context = ts;
 
                 m++;
@@ -791,7 +840,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                 x->len = 2;
                 spi_message_add_tail(x, m);
 
-                m->complete = ads7846_debounce;
+                m->complete = ads7846_rx_val;
                 m->context = ts;
         }
 
@@ -820,7 +869,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                         spi->dev.driver->name, ts)) {
                 dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
                 err = -EBUSY;
-                goto err_free_mem;
+                goto err_cleanup_filter;
         }
 
         dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
@@ -856,6 +905,9 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
  err_free_irq:
         free_irq(spi->irq, ts);
+ err_cleanup_filter:
+        if (ts->filter_cleanup)
+                ts->filter_cleanup(ts->filter_data);
  err_free_mem:
         input_free_device(input_dev);
         kfree(ts);
@@ -876,6 +928,9 @@ static int __devexit ads7846_remove(struct spi_device *spi)
         /* suspend left the IRQ disabled */
         enable_irq(ts->spi->irq);
 
+        if (ts->filter_cleanup)
+                ts->filter_cleanup(ts->filter_data);
+
         kfree(ts);
 
         dev_dbg(&spi->dev, "unregistered touchscreen\n");
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index adb3dafd33e9..1663f940ca11 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -5,6 +5,12 @@
  *
  * It's OK if the min/max values are zero.
  */
+enum ads7846_filter {
+        ADS7846_FILTER_OK,
+        ADS7846_FILTER_REPEAT,
+        ADS7846_FILTER_IGNORE,
+};
+
 struct ads7846_platform_data {
         u16     model;                  /* 7843, 7845, 7846. */
         u16     vref_delay_usecs;       /* 0 for external vref; etc */
@@ -21,5 +27,9 @@ struct ads7846_platform_data {
         u16     debounce_rep;           /* additional consecutive good readings
                                          * required after the first two */
         int     (*get_pendown_state)(void);
+        int     (*filter_init)  (struct ads7846_platform_data *pdata,
+                                 void **filter_data);
+        int     (*filter)       (void *filter_data, int data_idx, int *val);
+        void    (*filter_cleanup)(void *filter_data);
 };