mfd: ti_am335x_tscadc: Fix idle timeout value

[platform/kernel/linux-exynos.git] / include / linux / mfd / ti_am335x_tscadc.h

diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
index 25f2c61..4befdb8 100644 (file)
--- a/include/linux/mfd/ti_am335x_tscadc.h
+++ b/include/linux/mfd/ti_am335x_tscadc.h
@@ -125,13 +125,18 @@
 #define TOTAL_CHANNELS         8
 
 /*
-* ADC runs at 3MHz, and it takes
-* 15 cycles to latch one data output.
-* Hence the idle time for ADC to
-* process one sample data would be
-* around 5 micro seconds.
-*/
-#define IDLE_TIMEOUT 5 /* microsec */
+ * time in us for processing a single channel, calculated as follows:
+ *
+ * num cycles = open delay + (sample delay + conv time) * averaging
+ *
+ * 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 116 /* microsec */
 
 #define TSCADC_CELLS           2