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authorKrzysztof Kozlowski <krzk@kernel.org>2019-03-06 19:37:53 +0100
committerMinkyu Kang <mk7.kang@samsung.com>2019-03-11 15:53:19 +0900
commitfce86100606d14e53517a3601849646e69715465 (patch)
treee173fc703b4529c71c71aede601cceab823743e7 /board/samsung
parent345a53685f7dc7a8da8fbc1be596c02c7209bfbf (diff)
arm: exynos: Wait till ADC stabilizes before checking Odroid HC1 revision
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>
Diffstat (limited to 'board/samsung')
-rw-r--r--board/samsung/common/exynos5-dt-types.c38
1 files changed, 37 insertions, 1 deletions
diff --git a/board/samsung/common/exynos5-dt-types.c b/board/samsung/common/exynos5-dt-types.c
index 7c1271d654..516c32923e 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;