[media] si4713: Modified i2c driver to handle cases where interrupts are not used

Checks have been introduced at several places in the code to test if an
interrupt is set or not. For devices which do not use the interrupt, to
get a valid response, within a specified timeout, the device is polled
instead.
Signed-off-by: Dinesh Ram <dinesh.ram@cern.ch>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Eduardo Valentin <edubezval@gmail.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/radio/si4713/si4713.c

@@ -27,11 +27,11 @@
 #include <linux/i2c.h>
 #include <linux/slab.h>
 #include <linux/gpio.h>
-#include <linux/regulator/consumer.h>
 #include <linux/module.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-ioctl.h>
 #include <media/v4l2-common.h>
+#include <linux/regulator/consumer.h>
 
 #include "si4713.h"
 
@@ -213,6 +213,7 @@ static int si4713_send_command(struct si4713_device *sdev, const u8 command,
 				u8 response[], const int respn, const int usecs)
 {
 	struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
+	unsigned long until_jiffies;
 	u8 data1[MAX_ARGS + 1];
 	int err;
 
@@ -228,30 +229,39 @@ static int si4713_send_command(struct si4713_device *sdev, const u8 command,
 	if (err != argn + 1) {
 		v4l2_err(&sdev->sd, "Error while sending command 0x%02x\n",
 			command);
-		return (err > 0) ? -EIO : err;
+		return err < 0 ? err : -EIO;
 	}
 
+	until_jiffies = jiffies + usecs_to_jiffies(usecs) + 1;
+
 	/* Wait response from interrupt */
-	if (!wait_for_completion_timeout(&sdev->work,
+	if (client->irq) {
+		if (!wait_for_completion_timeout(&sdev->work,
 				usecs_to_jiffies(usecs) + 1))
-		v4l2_warn(&sdev->sd,
+			v4l2_warn(&sdev->sd,
 				"(%s) Device took too much time to answer.\n",
 				__func__);
-
-	/* Then get the response */
-	err = i2c_master_recv(client, response, respn);
-	if (err != respn) {
-		v4l2_err(&sdev->sd,
-			"Error while reading response for command 0x%02x\n",
-			command);
-		return (err > 0) ? -EIO : err;
 	}
 
-	DBG_BUFFER(&sdev->sd, "Response", response, respn);
-	if (check_command_failed(response[0]))
-		return -EBUSY;
+	do {
+		err = i2c_master_recv(client, response, respn);
+		if (err != respn) {
+			v4l2_err(&sdev->sd,
+				"Error %d while reading response for command 0x%02x\n",
+				err, command);
+			return err < 0 ? err : -EIO;
+		}
+
+		DBG_BUFFER(&sdev->sd, "Response", response, respn);
+		if (!check_command_failed(response[0]))
+			return 0;
 
-	return 0;
+		if (client->irq)
+			return -EBUSY;
+		msleep(1);
+	} while (jiffies <= until_jiffies);
+
+	return -EBUSY;
 }
 
 /*
@@ -344,14 +354,15 @@ static int si4713_write_property(struct si4713_device *sdev, u16 prop, u16 val)
  */
 static int si4713_powerup(struct si4713_device *sdev)
 {
+	struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
 	int err;
 	u8 resp[SI4713_PWUP_NRESP];
 	/*
 	 * 	.First byte = Enabled interrupts and boot function
 	 * 	.Second byte = Input operation mode
 	 */
-	const u8 args[SI4713_PWUP_NARGS] = {
-		SI4713_PWUP_CTSIEN | SI4713_PWUP_GPO2OEN | SI4713_PWUP_FUNC_TX,
+	u8 args[SI4713_PWUP_NARGS] = {
+		SI4713_PWUP_GPO2OEN | SI4713_PWUP_FUNC_TX,
 		SI4713_PWUP_OPMOD_ANALOG,
 	};
 
@@ -369,6 +380,9 @@ static int si4713_powerup(struct si4713_device *sdev)
 		gpio_set_value(sdev->gpio_reset, 1);
 	}
 
+	if (client->irq)
+		args[0] |= SI4713_PWUP_CTSIEN;
+
 	err = si4713_send_command(sdev, SI4713_CMD_POWER_UP,
 					args, ARRAY_SIZE(args),
 					resp, ARRAY_SIZE(resp),
@@ -380,7 +394,8 @@ static int si4713_powerup(struct si4713_device *sdev)
 		v4l2_dbg(1, debug, &sdev->sd, "Device in power up mode\n");
 		sdev->power_state = POWER_ON;
 
-		err = si4713_write_property(sdev, SI4713_GPO_IEN,
+		if (client->irq)
+			err = si4713_write_property(sdev, SI4713_GPO_IEN,
 						SI4713_STC_INT | SI4713_CTS);
 	} else {
 		if (gpio_is_valid(sdev->gpio_reset))
@@ -465,33 +480,39 @@ static int si4713_checkrev(struct si4713_device *sdev)
  */
 static int si4713_wait_stc(struct si4713_device *sdev, const int usecs)
 {
-	int err;
+	struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
 	u8 resp[SI4713_GET_STATUS_NRESP];
+	unsigned long start_jiffies = jiffies;
+	int err;
 
-	/* Wait response from STC interrupt */
-	if (!wait_for_completion_timeout(&sdev->work,
-			usecs_to_jiffies(usecs) + 1))
+	if (client->irq &&
+	    !wait_for_completion_timeout(&sdev->work, usecs_to_jiffies(usecs) + 1))
 		v4l2_warn(&sdev->sd,
-			"%s: device took too much time to answer (%d usec).\n",
-				__func__, usecs);
-
-	/* Clear status bits */
-	err = si4713_send_command(sdev, SI4713_CMD_GET_INT_STATUS,
-					NULL, 0,
-					resp, ARRAY_SIZE(resp),
-					DEFAULT_TIMEOUT);
-
-	if (err < 0)
-		goto exit;
-
-	v4l2_dbg(1, debug, &sdev->sd,
-			"%s: status bits: 0x%02x\n", __func__, resp[0]);
-
-	if (!(resp[0] & SI4713_STC_INT))
-		err = -EIO;
-
-exit:
-	return err;
+			"(%s) Device took too much time to answer.\n", __func__);
+
+	for (;;) {
+		/* Clear status bits */
+		err = si4713_send_command(sdev, SI4713_CMD_GET_INT_STATUS,
+				NULL, 0,
+				resp, ARRAY_SIZE(resp),
+				DEFAULT_TIMEOUT);
+		/* The USB device returns errors when it waits for the
+		 * STC bit to be set. Hence polling */
+		if (err >= 0) {
+			v4l2_dbg(1, debug, &sdev->sd,
+				"%s: status bits: 0x%02x\n", __func__, resp[0]);
+
+			if (resp[0] & SI4713_STC_INT)
+				return 0;
+		}
+		if (jiffies_to_usecs(jiffies - start_jiffies) > usecs)
+			return err < 0 ? err : -EIO;
+		/* We sleep here for 3 ms in order to avoid flooding the device
+		 * with USB requests. The si4713 USB driver was developed
+		 * by reverse engineering the Windows USB driver. The windows
+		 * driver also has a ~2.5 ms delay between responses. */
+		msleep(3);
+	}
 }
 
 /*
@@ -1024,7 +1045,6 @@ static int si4713_initialize(struct si4713_device *sdev)
 	if (rval < 0)
 		return rval;
 
-
 	sdev->frequency = DEFAULT_FREQUENCY;
 	sdev->stereo = 1;
 	sdev->tune_rnl = DEFAULT_TUNE_RNL;