iio: light: opt3001: enable operation w/o IRQ

Enable operation of the TI OPT3001 light sensor without having an
interrupt line available to connect the INT pin to.

In this operation mode, we issue a conversion request and simply wait
for the conversion time available as timeout value, determined from
integration time configuration and the worst-case time given in the data
sheet (sect. 6.5, table on p. 5):

  short integration time (100ms): 110ms + 3ms = 113ms
   long integration time (800ms): 880ms + 3ms = 883ms

This change is transparent as behaviour defaults to using the interrupt
method if an interrupt no. is configured via device tree. Interrupt-less
operation mode is performed when no valid interrupt no. is given.

Signed-off-by: Alexander Koch <mail@alexanderkoch.net>
Signed-off-by: Michael Hornung <mhornung.linux@gmail.com>
Tested-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 95 insertions, 42 deletions

diff --git a/drivers/iio/light/opt3001.c b/drivers/iio/light/opt3001.c
index b05c484a1646..b776c8ed4387 100644
--- a/drivers/iio/light/opt3001.c
+++ b/drivers/iio/light/opt3001.c
@@ -70,9 +70,12 @@
 
 /*
  * Time to wait for conversion result to be ready. The device datasheet
- * worst-case max value is 880ms. Add some slack to be on the safe side.
+ * sect. 6.5 states results are ready after total integration time plus 3ms.
+ * This results in worst-case max values of 113ms or 883ms, respectively.
+ * Add some slack to be on the safe side.
  */
-#define OPT3001_RESULT_READY_TIMEOUT    msecs_to_jiffies(1000)
+#define OPT3001_RESULT_READY_SHORT      150
+#define OPT3001_RESULT_READY_LONG       1000
 
 struct opt3001 {
         struct i2c_client       *client;
@@ -92,6 +95,8 @@ struct opt3001 {
 
         u8                      high_thresh_exp;
         u8                      low_thresh_exp;
+
+        bool                    use_irq;
 };
 
 struct opt3001_scale {
@@ -230,26 +235,30 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
         u16 reg;
         u8 exponent;
         u16 value;
+        long timeout;
 
-        /*
-         * Enable the end-of-conversion interrupt mechanism. Note that doing
-         * so will overwrite the low-level limit value however we will restore
-         * this value later on.
-         */
-        ret = i2c_smbus_write_word_swapped(opt->client, OPT3001_LOW_LIMIT,
-                        OPT3001_LOW_LIMIT_EOC_ENABLE);
-        if (ret < 0) {
-                dev_err(opt->dev, "failed to write register %02x\n",
-                                OPT3001_LOW_LIMIT);
-                return ret;
+        if (opt->use_irq) {
+                /*
+                 * Enable the end-of-conversion interrupt mechanism. Note that
+                 * doing so will overwrite the low-level limit value however we
+                 * will restore this value later on.
+                 */
+                ret = i2c_smbus_write_word_swapped(opt->client,
+                                        OPT3001_LOW_LIMIT,
+                                        OPT3001_LOW_LIMIT_EOC_ENABLE);
+                if (ret < 0) {
+                        dev_err(opt->dev, "failed to write register %02x\n",
+                                        OPT3001_LOW_LIMIT);
+                        return ret;
+                }
+
+                /* Allow IRQ to access the device despite lock being set */
+                opt->ok_to_ignore_lock = true;
         }
 
-        /* Reset data-ready indicator flag (will be set in the IRQ routine) */
+        /* Reset data-ready indicator flag */
         opt->result_ready = false;
 
-        /* Allow IRQ to access the device despite lock being set */
-        opt->ok_to_ignore_lock = true;
-
         /* Configure for single-conversion mode and start a new conversion */
         ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
         if (ret < 0) {
@@ -269,32 +278,69 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
                 goto err;
         }
 
-        /* Wait for the IRQ to indicate the conversion is complete */
-        ret = wait_event_timeout(opt->result_ready_queue, opt->result_ready,
-                        OPT3001_RESULT_READY_TIMEOUT);
+        if (opt->use_irq) {
+                /* Wait for the IRQ to indicate the conversion is complete */
+                ret = wait_event_timeout(opt->result_ready_queue,
+                                opt->result_ready,
+                                msecs_to_jiffies(OPT3001_RESULT_READY_LONG));
+        } else {
+                /* Sleep for result ready time */
+                timeout = (opt->int_time == OPT3001_INT_TIME_SHORT) ?
+                        OPT3001_RESULT_READY_SHORT : OPT3001_RESULT_READY_LONG;
+                msleep(timeout);
+
+                /* Check result ready flag */
+                ret = i2c_smbus_read_word_swapped(opt->client,
+                                                  OPT3001_CONFIGURATION);
+                if (ret < 0) {
+                        dev_err(opt->dev, "failed to read register %02x\n",
+                                OPT3001_CONFIGURATION);
+                        goto err;
+                }
+
+                if (!(ret & OPT3001_CONFIGURATION_CRF)) {
+                        ret = -ETIMEDOUT;
+                        goto err;
+                }
+
+                /* Obtain value */
+                ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_RESULT);
+                if (ret < 0) {
+                        dev_err(opt->dev, "failed to read register %02x\n",
+                                OPT3001_RESULT);
+                        goto err;
+                }
+                opt->result = ret;
+                opt->result_ready = true;
+        }
 
 err:
-        /* Disallow IRQ to access the device while lock is active */
-        opt->ok_to_ignore_lock = false;
+        if (opt->use_irq)
+                /* Disallow IRQ to access the device while lock is active */
+                opt->ok_to_ignore_lock = false;
 
         if (ret == 0)
                 return -ETIMEDOUT;
         else if (ret < 0)
                 return ret;
 
-        /*
-         * Disable the end-of-conversion interrupt mechanism by restoring the
-         * low-level limit value (clearing OPT3001_LOW_LIMIT_EOC_ENABLE). Note
-         * that selectively clearing those enable bits would affect the actual
-         * limit value due to bit-overlap and therefore can't be done.
-         */
-        value = (opt->low_thresh_exp << 12) | opt->low_thresh_mantissa;
-        ret = i2c_smbus_write_word_swapped(opt->client, OPT3001_LOW_LIMIT,
-                        value);
-        if (ret < 0) {
-                dev_err(opt->dev, "failed to write register %02x\n",
-                                OPT3001_LOW_LIMIT);
-                return ret;
+        if (opt->use_irq) {
+                /*
+                 * Disable the end-of-conversion interrupt mechanism by
+                 * restoring the low-level limit value (clearing
+                 * OPT3001_LOW_LIMIT_EOC_ENABLE). Note that selectively clearing
+                 * those enable bits would affect the actual limit value due to
+                 * bit-overlap and therefore can't be done.
+                 */
+                value = (opt->low_thresh_exp << 12) | opt->low_thresh_mantissa;
+                ret = i2c_smbus_write_word_swapped(opt->client,
+                                                   OPT3001_LOW_LIMIT,
+                                                   value);
+                if (ret < 0) {
+                        dev_err(opt->dev, "failed to write register %02x\n",
+                                        OPT3001_LOW_LIMIT);
+                        return ret;
+                }
         }
 
         exponent = OPT3001_REG_EXPONENT(opt->result);
@@ -736,12 +782,18 @@ static int opt3001_probe(struct i2c_client *client,
                 return ret;
         }
 
-        ret = request_threaded_irq(irq, NULL, opt3001_irq,
-                        IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
-                        "opt3001", iio);
-        if (ret) {
-                dev_err(dev, "failed to request IRQ #%d\n", irq);
-                return ret;
+        /* Make use of INT pin only if valid IRQ no. is given */
+        if (irq > 0) {
+                ret = request_threaded_irq(irq, NULL, opt3001_irq,
+                                IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+                                "opt3001", iio);
+                if (ret) {
+                        dev_err(dev, "failed to request IRQ #%d\n", irq);
+                        return ret;
+                }
+                opt->use_irq = true;
+        } else {
+                dev_dbg(opt->dev, "enabling interrupt-less operation\n");
         }
 
         return 0;
@@ -754,7 +806,8 @@ static int opt3001_remove(struct i2c_client *client)
         int ret;
         u16 reg;
 
-        free_irq(client->irq, iio);
+        if (opt->use_irq)
+                free_irq(client->irq, iio);
 
         ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
         if (ret < 0) {