iio: adc: cc10001: Power-up the ADC at probe time when used remotely

The ADC is typically shared with remote CPUs not running Linux.
However, there is only one register to power-up/power-down. Remote CPUs
aren't able to power-up the ADC, and rely in Linux doing it instead.

This commit uses the adc-reserved-channels devicetree property to
distinguish shared usage. In this case, the ADC is powered up at
probe time.

If the ADC is used only by the CPU running Linux, power-up/down
at runtime, only when neeeded.

Signed-off-by: Naidu Tellapati <naidu.tellapati@imgtec.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/adc/cc10001_adc.c b/drivers/iio/adc/cc10001_adc.c
index 115f6e9..8254f52 100644 (file)
--- a/drivers/iio/adc/cc10001_adc.c
+++ b/drivers/iio/adc/cc10001_adc.c
@@ -62,6 +62,7 @@ struct cc10001_adc_device {
        struct regulator *reg;
        u16 *buf;
 
+       bool shared;
        struct mutex lock;
        unsigned int start_delay_ns;
        unsigned int eoc_delay_ns;
@@ -153,7 +154,8 @@ static irqreturn_t cc10001_adc_trigger_h(int irq, void *p)
 
        mutex_lock(&adc_dev->lock);
 
-       cc10001_adc_power_up(adc_dev);
+       if (!adc_dev->shared)
+               cc10001_adc_power_up(adc_dev);
 
        /* Calculate delay step for eoc and sampled data */
        delay_ns = adc_dev->eoc_delay_ns / CC10001_MAX_POLL_COUNT;
@@ -177,7 +179,8 @@ static irqreturn_t cc10001_adc_trigger_h(int irq, void *p)
        }
 
 done:
-       cc10001_adc_power_down(adc_dev);
+       if (!adc_dev->shared)
+               cc10001_adc_power_down(adc_dev);
 
        mutex_unlock(&adc_dev->lock);
 
@@ -196,7 +199,8 @@ static u16 cc10001_adc_read_raw_voltage(struct iio_dev *indio_dev,
        unsigned int delay_ns;
        u16 val;
 
-       cc10001_adc_power_up(adc_dev);
+       if (!adc_dev->shared)
+               cc10001_adc_power_up(adc_dev);
 
        /* Calculate delay step for eoc and sampled data */
        delay_ns = adc_dev->eoc_delay_ns / CC10001_MAX_POLL_COUNT;
@@ -205,7 +209,8 @@ static u16 cc10001_adc_read_raw_voltage(struct iio_dev *indio_dev,
 
        val = cc10001_adc_poll_done(indio_dev, chan->channel, delay_ns);
 
-       cc10001_adc_power_down(adc_dev);
+       if (!adc_dev->shared)
+               cc10001_adc_power_down(adc_dev);
 
        return val;
 }
@@ -322,8 +327,10 @@ static int cc10001_adc_probe(struct platform_device *pdev)
        adc_dev = iio_priv(indio_dev);
 
        channel_map = GENMASK(CC10001_ADC_NUM_CHANNELS - 1, 0);
-       if (!of_property_read_u32(node, "adc-reserved-channels", &ret))
+       if (!of_property_read_u32(node, "adc-reserved-channels", &ret)) {
+               adc_dev->shared = true;
                channel_map &= ~ret;
+       }
 
        adc_dev->reg = devm_regulator_get(&pdev->dev, "vref");
        if (IS_ERR(adc_dev->reg))
@@ -368,6 +375,14 @@ static int cc10001_adc_probe(struct platform_device *pdev)
        adc_dev->eoc_delay_ns = NSEC_PER_SEC / adc_clk_rate;
        adc_dev->start_delay_ns = adc_dev->eoc_delay_ns * CC10001_WAIT_CYCLES;
 
+       /*
+        * There is only one register to power-up/power-down the AUX ADC.
+        * If the ADC is shared among multiple CPUs, always power it up here.
+        * If the ADC is used only by the MIPS, power-up/power-down at runtime.
+        */
+       if (adc_dev->shared)
+               cc10001_adc_power_up(adc_dev);
+
        /* Setup the ADC channels available on the device */
        ret = cc10001_adc_channel_init(indio_dev, channel_map);
        if (ret < 0)
@@ -402,6 +417,7 @@ static int cc10001_adc_remove(struct platform_device *pdev)
        struct iio_dev *indio_dev = platform_get_drvdata(pdev);
        struct cc10001_adc_device *adc_dev = iio_priv(indio_dev);
 
+       cc10001_adc_power_down(adc_dev);
        iio_device_unregister(indio_dev);
        iio_triggered_buffer_cleanup(indio_dev);
        clk_disable_unprepare(adc_dev->adc_clk);