Input: edt-ft5x06 - work around first register access error

The EP0700MLP1 returns bogus data on the first register read access
(reading the threshold parameter from register 0x00):

    edt_ft5x06 2-0038: crc error: 0xfc expected, got 0x40

It ignores writes until then. This patch adds a dummy read after which
the number of sensors and parameter read/writes work correctly.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
index d61731c..b87b1e0 100644 (file)
--- a/drivers/input/touchscreen/edt-ft5x06.c
+++ b/drivers/input/touchscreen/edt-ft5x06.c
@@ -1050,6 +1050,7 @@ static int edt_ft5x06_ts_probe(struct i2c_client *client,
 {
        const struct edt_i2c_chip_data *chip_data;
        struct edt_ft5x06_ts_data *tsdata;
+       u8 buf[2] = { 0xfc, 0x00 };
        struct input_dev *input;
        unsigned long irq_flags;
        int error;
@@ -1140,6 +1141,12 @@ static int edt_ft5x06_ts_probe(struct i2c_client *client,
                return error;
        }
 
+       /*
+        * Dummy read access. EP0700MLP1 returns bogus data on the first
+        * register read access and ignores writes.
+        */
+       edt_ft5x06_ts_readwrite(tsdata->client, 2, buf, 2, buf);
+
        edt_ft5x06_ts_set_regs(tsdata);
        edt_ft5x06_ts_get_defaults(&client->dev, tsdata);
        edt_ft5x06_ts_get_parameters(tsdata);