Am 15.02.2017 um 00:16 schrieb Martin Blumenstingl:

Hi Heiner,

thanks for this patch!
I have some questions since I don't have access to my boards until
Saturday - I added them inline below.

On Tue, Feb 14, 2017 at 10:58 PM, Heiner Kallweit [off-list ref] wrote:

quoted

Switch from polling to interrupt mode.

Successfully tested on a S905GXBB-based Odroid C2.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/iio/adc/meson_saradc.c | 46 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index 89def603..dbd56bcc 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c

@@ -18,7 +18,9 @@
 #include <linux/io.h>
 #include <linux/iio/iio.h>
 #include <linux/module.h>
+#include <linux/interrupt.h>
 #include <linux/of.h>
+#include <linux/of_irq.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>

@@ -163,6 +165,7 @@
        #define MESON_SAR_ADC_REG13_12BIT_CALIBRATION_MASK      GENMASK(13, 8)

 #define MESON_SAR_ADC_MAX_FIFO_SIZE                            32
+#define MESON_SAR_ADC_TIMEOUT                                  100 /* ms */

 #define MESON_SAR_ADC_CHAN(_chan) {                                    \
        .type = IIO_VOLTAGE,                                            \

@@ -229,6 +232,7 @@ struct meson_sar_adc_priv {
        struct clk_gate                         clk_gate;
        struct clk                              *adc_div_clk;
        struct clk_divider                      clk_div;
+       struct completion                       done;
 };

 static const struct regmap_config meson_sar_adc_regmap_config = {

@@ -274,11 +278,11 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
                                         int *val)
 {
        struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
-       int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
+       int regval, fifo_chan, fifo_val, sum = 0, count = 0;

-       ret = meson_sar_adc_wait_busy_clear(indio_dev);
-       if (ret)
-               return ret;
+       if(!wait_for_completion_timeout(&priv->done,
+                               msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
+               return -ETIMEDOUT;

        while (meson_sar_adc_get_fifo_count(indio_dev) > 0 &&
               count < MESON_SAR_ADC_MAX_FIFO_SIZE) {

@@ -456,6 +460,7 @@ static int meson_sar_adc_get_sample(struct iio_dev *indio_dev,
                                    enum meson_sar_adc_num_samples avg_samples,
                                    int *val)
 {
+       struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
        int ret;

        ret = meson_sar_adc_lock(indio_dev);

@@ -465,6 +470,11 @@ static int meson_sar_adc_get_sample(struct iio_dev *indio_dev,
        /* clear the FIFO to make sure we're not reading old values */
        meson_sar_adc_clear_fifo(indio_dev);

+       reinit_completion(&priv->done);
+       regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+                          MESON_SAR_ADC_REG0_FIFO_IRQ_EN,
+                          MESON_SAR_ADC_REG0_FIFO_IRQ_EN);
+

can't we add this to meson_sar_adc_start_sample_engine()?

quoted

        meson_sar_adc_set_averaging(indio_dev, chan, avg_mode, avg_samples);

        meson_sar_adc_enable_channel(indio_dev, chan);

@@ -473,6 +483,9 @@ static int meson_sar_adc_get_sample(struct iio_dev *indio_dev,
        ret = meson_sar_adc_read_raw_sample(indio_dev, chan, val);
        meson_sar_adc_stop_sample_engine(indio_dev);

+       regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+                          MESON_SAR_ADC_REG0_FIFO_IRQ_EN, 0);
+

similar to enabling the IRQ above, can't we add this to
meson_sar_adc_stop_sample_engine()?

quoted

        meson_sar_adc_unlock(indio_dev);

        if (ret) {

@@ -577,6 +590,9 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
         */
        meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);

+       regval = FIELD_PREP(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, 1);
+       regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+                          MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);

I'm wondering whether we should do this in meson_sar_adc_hw_enable()
in case u-boot is involved in the "return from suspend" process then
doing it in _init() might be a problem since the vendor u-boot
overwrites REG0, see [0]
please note that this is an actual question, not some kind of
suggestion in question form

At a first glance I couldn't see that in uboot saradc_enable is used
somewhere in the boot process. There seems to be a uboot command line
command triggering saradc_enable.
But I'm no expert at all to which extent uboot is involved in system
suspend / resume, so I might miss something.

Moving this register initialization to meson_sar_adc_hw_enable()
doesn't hurt and we're safe in case the scenario you described
can actually occur. So I'd go for it.

quoted

        /*
         * leave sampling delay and the input clocks as configured by BL30 to
         * make sure BL30 gets the values it expects when reading the

@@ -728,6 +744,16 @@ static int meson_sar_adc_hw_disable(struct iio_dev *indio_dev)
        return 0;
 }

+static irqreturn_t meson_sar_adc_irq(int irq, void *data)
+{
+       struct iio_dev *indio_dev = data;
+       struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
+
+       complete(&priv->done);
+
+       return IRQ_HANDLED;

would it make sense to return IRQ_NONE when
meson_sar_adc_get_fifo_count() returns 0?

quoted

+}
+
 static const struct iio_info meson_sar_adc_iio_info = {
        .read_raw = meson_sar_adc_iio_info_read_raw,
        .driver_module = THIS_MODULE,

@@ -770,7 +796,7 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
        struct resource *res;
        void __iomem *base;
        const struct of_device_id *match;
-       int ret;
+       int irq, ret;

        indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
        if (!indio_dev) {

@@ -779,6 +805,7 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
        }

        priv = iio_priv(indio_dev);
+       init_completion(&priv->done);

        match = of_match_device(meson_sar_adc_of_match, &pdev->dev);
        priv->data = match->data;

@@ -797,6 +824,15 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
        if (IS_ERR(base))
                return PTR_ERR(base);

+       irq = irq_of_parse_and_map(pdev->dev.of_node, 0);

Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt
should also be updated to reflect that the IRQ is now required (the
.dts already contains the IRQ, so no change is required on that side).

quoted

+       if (!irq)
+               return -EINVAL;
+
+       ret = devm_request_irq(&pdev->dev, irq, meson_sar_adc_irq, 0,
+                              dev_name(&pdev->dev), indio_dev);
+       if (ret)
+               return ret;
+
        priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
                                             &meson_sar_adc_regmap_config);
        if (IS_ERR(priv->regmap))
--
2.11.1

Regards,
Martin

[0] https://github.com/khadas/u-boot/blob/d09ed9f0c69054e46af45a7aed2b3cb0f6eaa3bc/drivers/adc/saradc.c#L191