input: touchscreen: edt-ft5x06: Suppress bogus data on startup

When polled without the use of IRQ, FT5x06 registers may return
undefined initial data, causing unwanted touches or event spamming.
A simple way to filter this out is to suppress touches until the
TD_STATUS register changes for the first time.

Increase the delay before first polling to 300ms, to avoid
transient I2C read flakiness that seems to occur after reset.

Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>

diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
index 9541609..9c7fdbb 100644 (file)
--- a/drivers/input/touchscreen/edt-ft5x06.c
+++ b/drivers/input/touchscreen/edt-ft5x06.c
@@ -80,6 +80,8 @@
 #define M06_REG_CMD(factory) ((factory) ? 0xf3 : 0xfc)
 #define M06_REG_ADDR(factory, addr) ((factory) ? (addr) & 0x7f : (addr) & 0x3f)
 
+#define RESET_DELAY_MS                 300     /* reset deassert to I2C */
+#define FIRST_POLL_DELAY_MS            300     /* in addition to the above */
 #define POLL_INTERVAL_MS               17      /* 17ms = 60fps */
 
 enum edt_pmode {
@@ -145,6 +147,7 @@ struct edt_ft5x06_ts_data {
 
        char name[EDT_NAME_LEN];
        char fw_version[EDT_NAME_LEN];
+       int init_td_status;
 
        struct edt_reg_addr reg_addr;
        enum edt_ver version;
@@ -324,6 +327,21 @@ static irqreturn_t edt_ft5x06_ts_isr(int irq, void *dev_id)
                 * points.
                 */
                num_points = min(rdbuf[2] & 0xf, tsdata->max_support_points);
+
+               /* When polling FT5x06 without IRQ: initial register contents
+                * could be stale or undefined; discard all readings until
+                * TD_STATUS changes for the first time (or num_points is 0).
+                */
+               if (tsdata->init_td_status) {
+                       if (tsdata->init_td_status < 0)
+                               tsdata->init_td_status = rdbuf[2];
+
+                       if (num_points && rdbuf[2] == tsdata->init_td_status)
+                               goto out;
+
+                       tsdata->init_td_status = 0;
+               }
+
                if (!error && num_points)
                        error = regmap_bulk_read(tsdata->regmap,
                                                 tsdata->tdata_offset,
@@ -1300,7 +1318,7 @@ static int edt_ft5x06_ts_probe(struct i2c_client *client)
        if (tsdata->reset_gpio) {
                usleep_range(5000, 6000);
                gpiod_set_value_cansleep(tsdata->reset_gpio, 0);
-               msleep(300);
+               msleep(RESET_DELAY_MS);
        }
 
        input = devm_input_allocate_device(&client->dev);
@@ -1389,11 +1407,12 @@ static int edt_ft5x06_ts_probe(struct i2c_client *client)
                        return error;
                }
        } else {
+               tsdata->init_td_status = -1; /* filter bogus initial data */
                INIT_WORK(&tsdata->work_i2c_poll,
                          edt_ft5x06_ts_work_i2c_poll);
                timer_setup(&tsdata->timer, edt_ft5x06_ts_irq_poll_timer, 0);
-               tsdata->timer.expires = jiffies +
-                                       msecs_to_jiffies(POLL_INTERVAL_MS);
+               tsdata->timer.expires =
+                       jiffies + msecs_to_jiffies(FIRST_POLL_DELAY_MS);
                add_timer(&tsdata->timer);
        }