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 krzk@kernel.org Tested-by: Anand Moon linux.amoon@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;