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>

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 {
@@ -230,13 +235,16 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
 	u16 reg;
 	u8 exponent;
 	u16 value;
+	long timeout;
 
+	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.
+		 * 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,
+		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",
@@ -244,11 +252,12 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
 			return ret;
 		}
 
-	/* Reset data-ready indicator flag (will be set in the IRQ routine) */
-	opt->result_ready = false;
-
 		/* Allow IRQ to access the device despite lock being set */
 		opt->ok_to_ignore_lock = true;
+	}
+
+	/* Reset data-ready indicator flag */
+	opt->result_ready = false;
 
 	/* Configure for single-conversion mode and start a new conversion */
 	ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
@@ -269,11 +278,44 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
 		goto err;
 	}
 
+	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,
-			OPT3001_RESULT_READY_TIMEOUT);
+		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:
+	if (opt->use_irq)
 		/* Disallow IRQ to access the device while lock is active */
 		opt->ok_to_ignore_lock = false;
 
@@ -282,20 +324,24 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
 	else if (ret < 0)
 		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.
+		 * 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,
+		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);
 	mantissa = OPT3001_REG_MANTISSA(opt->result);
@@ -736,6 +782,8 @@ static int opt3001_probe(struct i2c_client *client,
 		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);
@@ -743,6 +791,10 @@ static int opt3001_probe(struct i2c_client *client,
 			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;
 }
@@ -754,6 +806,7 @@ static int opt3001_remove(struct i2c_client *client)
 	int ret;
 	u16 reg;
 
+	if (opt->use_irq)
 		free_irq(client->irq, iio);
 
 	ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);