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iio: aspeed-adc: wait for initial sequence.

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This patch enables adc engine at initialization time and waits
for the initial sequence completion before enabling adc channels.

Without this code adc channels are not functional and shows
zeros for all connected channels.

Tested on mellanox msn platform.

v1 -> v2:
Pointed by Rick Altherr:
 - Wait init sequence code enabled by bool
from OF match table.

Signed-off-by: Mykola Kostenok <c_mykolak@mellanox.com>
Reviewed-by: Rick Altherr <raltherr@google.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Mykola Kostenok 2017-07-17 12:00:35 +03:00 committed by Jonathan Cameron
parent e59e18989c
commit 737cc2a593
1 changed files with 26 additions and 0 deletions
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26
drivers/iio/adc/aspeed_adc.c
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@ -22,6 +22,7 @@
#include <linux/iio/iio.h>
#include <linux/iio/driver.h>
#include <linux/iopoll.h>
#define ASPEED_RESOLUTION_BITS 10
#define ASPEED_CLOCKS_PER_SAMPLE 12
@ -38,11 +39,17 @@
#define ASPEED_ENGINE_ENABLE BIT(0)
#define ASPEED_ADC_CTRL_INIT_RDY BIT(8)
#define ASPEED_ADC_INIT_POLLING_TIME 500
#define ASPEED_ADC_INIT_TIMEOUT 500000
struct aspeed_adc_model_data {
const char *model_name;
unsigned int min_sampling_rate; // Hz
unsigned int max_sampling_rate; // Hz
unsigned int vref_voltage; // mV
bool wait_init_sequence;
};
struct aspeed_adc_data {
@ -211,6 +218,24 @@ static int aspeed_adc_probe(struct platform_device *pdev)
goto scaler_error;
}
model_data = of_device_get_match_data(&pdev->dev);
if (model_data->wait_init_sequence) {
/* Enable engine in normal mode. */
writel(ASPEED_OPERATION_MODE_NORMAL | ASPEED_ENGINE_ENABLE,
data->base + ASPEED_REG_ENGINE_CONTROL);
/* Wait for initial sequence complete. */
ret = readl_poll_timeout(data->base + ASPEED_REG_ENGINE_CONTROL,
adc_engine_control_reg_val,
adc_engine_control_reg_val &
ASPEED_ADC_CTRL_INIT_RDY,
ASPEED_ADC_INIT_POLLING_TIME,
ASPEED_ADC_INIT_TIMEOUT);
if (ret)
goto scaler_error;
}
/* Start all channels in normal mode. */
clk_prepare_enable(data->clk_scaler->clk);
adc_engine_control_reg_val = GENMASK(31, 16) |
@ -270,6 +295,7 @@ static const struct aspeed_adc_model_data ast2500_model_data = {
.vref_voltage = 1800, // mV
.min_sampling_rate = 1,
.max_sampling_rate = 1000000,
.wait_init_sequence = true,
};
static const struct of_device_id aspeed_adc_matches[] = {