iio: mxs-lradc: change the realbits to 12

The LRADC virtual channels have an 18 bit field to store the sum of up
to 2^5 accumulated samples. The read_raw function however only operates
over a single sample (12 bit resolution).
In order to use this field for scaling operations, we need it to be the
exact resolution value of the LRADC.
Besides, the driver was using an 18 bit mask (LRADC_CH_VALUE_MASK) to
report touch coordinates to userland. A 12 bit mask should be used instead
or else the touch libraries will expect a coordinates range between 0
and 0x3ffff (18 bits), instead of between 0 and 0xfff (12 bits).

Signed-off-by: Hector Palacios <hector.palacios@digi.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 863f0861b7290692005c70032ead29d813564757..a08c1736458b4f2cfab9af87c408a65e430d8020 100644 (file)
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -225,6 +225,9 @@ struct mxs_lradc {
 #define        LRADC_CTRL4_LRADCSELECT_MASK(n)         (0xf << ((n) * 4))
 #define        LRADC_CTRL4_LRADCSELECT_OFFSET(n)       ((n) * 4)
 
+#define LRADC_RESOLUTION                       12
+#define LRADC_SINGLE_SAMPLE_MASK               ((1 << LRADC_RESOLUTION) - 1)
+
 /*
  * Raw I/O operations
  */
@@ -540,9 +543,10 @@ static int mxs_lradc_ts_register(struct mxs_lradc *lradc)
        __set_bit(EV_ABS, input->evbit);
        __set_bit(EV_KEY, input->evbit);
        __set_bit(BTN_TOUCH, input->keybit);
-       input_set_abs_params(input, ABS_X, 0, LRADC_CH_VALUE_MASK, 0, 0);
-       input_set_abs_params(input, ABS_Y, 0, LRADC_CH_VALUE_MASK, 0, 0);
-       input_set_abs_params(input, ABS_PRESSURE, 0, LRADC_CH_VALUE_MASK, 0, 0);
+       input_set_abs_params(input, ABS_X, 0, LRADC_SINGLE_SAMPLE_MASK, 0, 0);
+       input_set_abs_params(input, ABS_Y, 0, LRADC_SINGLE_SAMPLE_MASK, 0, 0);
+       input_set_abs_params(input, ABS_PRESSURE, 0, LRADC_SINGLE_SAMPLE_MASK,
+                            0, 0);
 
        lradc->ts_input = input;
        input_set_drvdata(input, lradc);
@@ -817,7 +821,7 @@ static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
        .channel = (idx),                                       \
        .scan_type = {                                          \
                .sign = 'u',                                    \
-               .realbits = 18,                                 \
+               .realbits = LRADC_RESOLUTION,                   \
                .storagebits = 32,                              \
        },                                                      \
 }