From mboxrd@z Thu Jan 1 00:00:00 1970 From: Krzysztof Kozlowski Date: Tue, 5 Mar 2019 20:57:58 +0100 Subject: [U-Boot] [PATCH v4 5/9] arm: exynos: Wait till ADC stabilizes before checking Odroid HC1 revision In-Reply-To: <20190305195802.14397-1-krzk@kernel.org> References: <20190305195802.14397-1-krzk@kernel.org> Message-ID: <20190305195802.14397-6-krzk@kernel.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de 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 Tested-by: Anand Moon --- 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