On Wed, 13 Feb 2019 17:46:44 +0100 Krzysztof Kozlowski krzk@kernel.org wrote:
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 be patient and wait for it to stabilize.
First reads on Odroid HC1 return 305, 1207, 1297 and finally 1308 (reference value is 1309).
Signed-off-by: Krzysztof Kozlowski krzk@kernel.org
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 af711e727a78..8aed64183837 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;- }
Is there in the documentation any required time to wait before reading the ADC value?
If yes then maybe get_timer() based approach shall be used (if get_timer() is available in this context)?
Please see for example drivers/net/fec_mxc.c for how timeouts are handled there.
I will test this patch series on XU3 during the weekend. Thanks for this fix :-)
- 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;
Best regards,
Lukasz Majewski
--
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