Hello,
On 07/05/2013 03:10 PM, Marek Vasut wrote:
Dear Hector Palacios,
Dear Marek,
On 07/05/2013 01:37 PM, Marek Vasut wrote:
Dear Hector Palacios,
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.
How would this work once the accumulation is supported?
As I see it, when you read a channel the driver should give you the 12-bit
value either of one single sample or of N samples.
The hardware will always give you 18 bit value, let's call it A of N accumulated
samples, each 12 bit long. N is in range of 1 to 32 .
The driver currently supports N = 1.
Do I understand it correctly that if we want to support N > 1, we have to do the
division of A / N in the driver and therefore we will again report only a 12-bit
value to the userland ?
If so,
Acked-by: Marek Vasut <marex@xxxxxxx>
Coming back to this patch, I just noticed that it is not enough to just change the
realbits from 18 to 12. When using this driver as touchscreen for Yocto's SATO graphic
rootfs I noticed that the driver is using LRADC_CH_VALUE_MASK for reporting the
coordinates.
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);
which is defined as an 18bit mask:
#define LRADC_CH_VALUE_MASK 0x3ffff
The result is that the touch calibration range in Xorg is expecting values between 0
and 262143 (0x3ffff), which causes trouble (at least I had problems to calibrate it).
root@computer:~# xinput --list mxs-lradc
mxs-lradc id=6 [slave pointer (2)]
Reporting 4 classes:
Class originated from: 6. Type: XIButtonClass
Buttons supported: 5
Button labels: "Button Unknown" "Button Unknown" "Button Unknown"
"Button Wheel Up" "Button Wheel Down"
Button state:
Class originated from: 6. Type: XIValuatorClass
Detail for Valuator 0:
Label: Abs X
Range: 0.000000 - 262143.000000
Resolution: 0 units/m
Mode: absolute
Current value: 2512.000000
Class originated from: 6. Type: XIValuatorClass
Detail for Valuator 1:
Label: Abs Y
Range: 0.000000 - 262143.000000
Resolution: 0 units/m
Mode: absolute
Current value: 1688.000000
Class originated from: 6. Type: XIValuatorClass
Detail for Valuator 2:
Label: Abs Pressure
Range: 0.000000 - 262143.000000
Resolution: 0 units/m
Mode: absolute
Current value: 0.000000
So probably we should complete this patch with the following:
diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 407a124..d2a0a83 100644
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -275,6 +275,9 @@ 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)
+
static int mxs_lradc_read_single(struct iio_dev *iio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long m)
@@ -737,9 +740,10 @@ 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);
@@ -1014,7 +1018,7 @@ static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
.address = (idx), \
.scan_type = { \
.sign = 'u', \
- .realbits = 18, \
+ .realbits = LRADC_RESOLUTION, \
.storagebits = 32, \
}, \
}
Notice that I leave the existing LRADC_CH_VALUE_MASK 18bit mask in the rest of the
driver, to support accumulated samples.
Curiously, ts_lib works fine without this (maybe the calibration fixes this?), but
nevertheless the information passed by the driver is incorrect, I guess.
Is anybody out there working with the touch? Under which graphic system?
Best regards,
--
Hector Palacios
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