From: Billy Tsai <billy_tsai@aspeedtech.com>
To: <jic23@kernel.org>, <lars@metafoo.de>, <pmeerw@pmeerw.net>,
<robh+dt@kernel.org>, <joel@jms.id.au>, <andrew@aj.id.au>,
<p.zabel@pengutronix.de>, <billy_tsai@aspeedtech.com>,
<linux-iio@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-aspeed@lists.ozlabs.org>, <raltherr@google.com>
Cc: <BMC-SW@aspeedtech.com>
Subject: [v1 6/7] iio: adc: aspeed: Add compensation phase.
Date: Mon, 19 Jul 2021 16:06:06 +0800 [thread overview]
Message-ID: <20210719080607.28712-7-billy_tsai@aspeedtech.com> (raw)
In-Reply-To: <20210719080607.28712-1-billy_tsai@aspeedtech.com>
This patch adds a compensation phase to improve the accurate of adc
measurement. This is the builtin function though input half of the
reference voltage to get the adc offset.
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
drivers/iio/adc/aspeed_adc.c | 51 +++++++++++++++++++++++++++++++++++-
1 file changed, 50 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
index b33ff9f0a3af..b0d7a58cb7f5 100644
--- a/drivers/iio/adc/aspeed_adc.c
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -56,6 +56,7 @@
#define ASPEED_ADC_INIT_POLLING_TIME 500
#define ASPEED_ADC_INIT_TIMEOUT 500000
#define ASPEED_ADC_DEF_SAMPLING_RATE 250000
+#define ASPEED_ADC_MAX_RAW_DATA GENMASK(9, 0)
enum aspeed_adc_version {
aspeed_adc_ast2400,
@@ -79,6 +80,7 @@ struct aspeed_adc_data {
struct reset_control *rst;
int vref;
u32 sample_period_ns;
+ int cv;
};
#define ASPEED_CHAN(_idx, _data_reg_addr) { \
@@ -110,6 +112,48 @@ static const struct iio_chan_spec aspeed_adc_iio_channels[] = {
ASPEED_CHAN(15, 0x2E),
};
+static int aspeed_adc_compensation(struct platform_device *pdev)
+{
+ struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+ struct aspeed_adc_data *data = iio_priv(indio_dev);
+ u32 index, adc_raw = 0;
+ u32 adc_engine_control_reg_val =
+ readl(data->base + ASPEED_REG_ENGINE_CONTROL);
+ adc_engine_control_reg_val |=
+ (ASPEED_ADC_OPERATION_MODE_NORMAL | ASPEED_ADC_ENGINE_ENABLE);
+
+ /*
+ * Enable compensating sensing:
+ * After that, the input voltage of adc will force to half of the reference
+ * voltage. So the expected reading raw data will become half of the max
+ * value. We can get compensating value = 0x200 - adc read raw value.
+ * It is recommended to average at least 10 samples to get a final CV.
+ */
+ writel(adc_engine_control_reg_val | ASPEED_ADC_CTRL_COMPENSATION |
+ ASPEED_ADC_CTRL_CHANNEL_ENABLE(0),
+ data->base + ASPEED_REG_ENGINE_CONTROL);
+ /*
+ * After enable compensating sensing mode need to wait some time for adc stable
+ * Experiment result is 1ms.
+ */
+ mdelay(1);
+
+ for (index = 0; index < 16; index++) {
+ /*
+ * Waiting for the sampling period ensures that the value acquired
+ * is fresh each time.
+ */
+ ndelay(data->sample_period_ns);
+ adc_raw += readw(data->base + aspeed_adc_iio_channels[0].address);
+ }
+ adc_raw >>= 4;
+ data->cv = BIT(ASPEED_RESOLUTION_BITS - 1) - adc_raw;
+ writel(adc_engine_control_reg_val,
+ data->base + ASPEED_REG_ENGINE_CONTROL);
+ dev_dbg(data->dev, "compensating value = %d\n", data->cv);
+ return 0;
+}
+
static int aspeed_adc_set_sampling_rate(struct iio_dev *indio_dev, u32 rate)
{
struct aspeed_adc_data *data = iio_priv(indio_dev);
@@ -138,7 +182,11 @@ static int aspeed_adc_read_raw(struct iio_dev *indio_dev,
switch (mask) {
case IIO_CHAN_INFO_RAW:
- *val = readw(data->base + chan->address);
+ *val = readw(data->base + chan->address) + data->cv;
+ if (*val < 0)
+ *val = 0;
+ else if (*val >= ASPEED_ADC_MAX_RAW_DATA)
+ *val = ASPEED_ADC_MAX_RAW_DATA;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
@@ -338,6 +386,7 @@ static int aspeed_adc_probe(struct platform_device *pdev)
if (ret)
goto clk_enable_error;
aspeed_adc_set_sampling_rate(indio_dev, ASPEED_ADC_DEF_SAMPLING_RATE);
+ aspeed_adc_compensation(pdev);
adc_engine_control_reg_val =
readl(data->base + ASPEED_REG_ENGINE_CONTROL);
/* Start all channels in normal mode. */
--
2.25.1
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next prev parent reply other threads:[~2021-07-19 8:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 8:06 [v1 0/7] Add support for ast2600 ADC Billy Tsai
2021-07-19 8:06 ` [v1 1/7] dt-bindings: iio: adc: rename the aspeed adc yaml Billy Tsai
2021-07-19 8:06 ` [v1 2/7] dt-bindings: iio: adc: Binding ast2600 adc Billy Tsai
2021-07-19 8:06 ` [v1 3/7] iio: adc: aspeed: completes the bitfield declare Billy Tsai
2021-07-19 8:06 ` [v1 4/7] iio: adc: aspeed: Allow driver to support ast2600 Billy Tsai
2021-07-19 8:06 ` [v1 5/7] iio: adc: aspeed: Add func to set sampling rate Billy Tsai
2021-07-19 8:06 ` Billy Tsai [this message]
2021-07-19 8:06 ` [v1 7/7] iio: adc: aspeed: Fix the calculate error of clock Billy Tsai
2021-07-24 16:24 ` [v1 0/7] Add support for ast2600 ADC Jonathan Cameron
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