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arm: exynos: Wait till ADC stabilizes before checking Odroid HC1 revision

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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>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
This commit is contained in:
Krzysztof Kozlowski 2019-03-06 19:37:53 +01:00 committed by Minkyu Kang
parent 345a53685f
commit fce8610060
1 changed files with 37 additions and 1 deletions
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38
board/samsung/common/exynos5-dt-types.c
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@ -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;