Fix detection of Odroid HC1 (Exynos5422) after reboot if kernel disabled
the LDO4/VDD_ADC regulator.
The LDO4 supplies both ADC block and the ADC input AIN9. Voltage on
AIN9 will rise slowly, so use delay of 5 milliseconds instead of
timers-based loop to wait for voltage stabilization.
First reads on Odroid HC1 return 305, 1207, 1297 and finally 1308
(reference value is 1309).
Signed-off-by: Krzysztof Kozlowski <k...@kernel.org>
Tested-by: Anand Moon <linux.am...@gmail.com>
---
board/samsung/common/exynos5-dt-types.c | 38 ++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/board/samsung/common/exynos5-dt-types.c
b/board/samsung/common/exynos5-dt-types.c
index 7c1271d6547a..516c32923e44 100644
--- a/board/samsung/common/exynos5-dt-types.c
+++ b/board/samsung/common/exynos5-dt-types.c
@@ -57,12 +57,48 @@ static unsigned int odroid_get_rev(void)
return 0;
}
+/*
+ * Read ADC at least twice and check the resuls. If regulator providing
voltage
+ * on to measured point was just turned on, first reads might require time
+ * to stabilize.
+ */
+static int odroid_get_adc_val(unsigned int *adcval)
+{
+ unsigned int adcval_prev = 0;
+ int ret, retries = 20;
+
+ ret = adc_channel_single_shot("adc", CONFIG_ODROID_REV_AIN,
+ &adcval_prev);
+ if (ret)
+ return ret;
+
+ while (retries--) {
+ mdelay(5);
+
+ ret = adc_channel_single_shot("adc", CONFIG_ODROID_REV_AIN,
+ adcval);
+ if (ret)
+ return ret;
+
+ /*
+ * If difference between ADC reads is less than 3%,
+ * accept the result
+ */
+ if ((100 * abs(*adcval - adcval_prev) / adcval_prev) < 3)
+ return ret;
+
+ adcval_prev = *adcval;
+ }
+
+ return ret;
+}
+
static int odroid_get_board_type(void)
{
unsigned int adcval;
int ret, i;
- ret = adc_channel_single_shot("adc", CONFIG_ODROID_REV_AIN, &adcval);
+ ret = odroid_get_adc_val(&adcval);
if (ret)
goto rev_default;
--
2.17.1
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