evie/android_kernel_oneplus_msm8998
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

mfd: ti_am335x_tscadc: Fix idle timeout value

Browse source 
The old timeout value was based on the assumption that the minimum values are
used for the open and sample delay and no averaging is done. In fact the ADC
and touchscreen driver both use an open delay of 152 cycles and averaging over
16 samples. This patch adjusts the timeout value accordingly

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Matthias Kaehlcke 2013-09-10 23:02:18 +02:00 • committed by Lee Jones
parent ecf67ac335
commit 1a54b7dabf
1 changed files with 12 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
include/linux/mfd/ti_am335x_tscadc.h
View file

@ -125,13 +125,18 @@
#define TOTAL_CHANNELS 8 #define TOTAL_CHANNELS 8
/* /*
* ADC runs at 3MHz, and it takes * time in us for processing a single channel, calculated as follows:
* 15 cycles to latch one data output. *
* Hence the idle time for ADC to * num cycles = open delay + (sample delay + conv time) * averaging
* process one sample data would be *
* around 5 micro seconds. * num cycles: 152 + (1 + 13) * 16 = 376
*
* clock frequency: 26MHz / 8 = 3.25MHz
* clock period: 1 / 3.25MHz = 308ns
*
* processing time: 376 * 308ns = 116us
*/ */
#define IDLE_TIMEOUT 5 /* microsec */ #define IDLE_TIMEOUT 116 /* microsec */
#define TSCADC_CELLS 2 #define TSCADC_CELLS 2