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w1_therm: release the bus during conversion on externally powered devices

PATCH In review Maciej Szmigiero 2 participants 2 messages Nov 15, 2011 – Nov 17, 2011 W1 dallas's 1-wire bus

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Maciej Szmigiero

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PATCH 1/1 w1_therm: release the bus during conversion on externally powered devices

w1_therm devices can either be bus powered or externally powered.

When device is bus powered during temperature conversion the bus have to be left high to provide necessary power. Some masters also allow strong power-up to be enabled in this case.
Naturally, no communication over bus can occur during that time.

However, if device has external power then there is no such restriction, and host can talk to other devices during temperature conversion.

There is command which allows us to check how device is powered, this patch uses it to release the bus on externally w1_therm powered devices during temperature conversion.

Also, this changes uninterruptible sleeps there into interruptible ones to avoid long uninterruptible sleep if w1 subsystem happens to grab bus for scan during w1_therm_read().

Signed-off-by Maciej Szmigiero <[email protected]>
drivers/w1/slaves/w1_therm.c +31 -5
index a1ef9b5..ff29ae7 100644
@@ -175,11 +175,13 @@ static ssize_t w1_therm_read(struct device *device,
 {
 	struct w1_slave *sl = dev_to_w1_slave(device);
 	struct w1_master *dev = sl->master;
-	u8 rom[9], crc, verdict;
+	u8 rom[9], crc, verdict, external_power;
 	int i, max_trying = 10;
 	ssize_t c = PAGE_SIZE;
 
-	mutex_lock(&dev->mutex);
+	i = mutex_lock_interruptible(&dev->mutex);
+	if (i != 0)
+		return i;
 
 	memset(rom, 0, sizeof(rom));
 

@@ -190,13 +192,37 @@ static ssize_t w1_therm_read(struct device *device,
 		if (!w1_reset_select_slave(sl)) {
 			int count = 0;
 			unsigned int tm = 750;
+			unsigned long sleep_rem;
+
+			w1_write_8(dev, W1_READ_PSUPPLY);
+			external_power = w1_read_8(dev);
+
+			if (w1_reset_select_slave(sl))
+				continue;
 
 			/* 750ms strong pullup (or delay) after the convert */
-			if (w1_strong_pullup)
+			if (!external_power && w1_strong_pullup)
 				w1_next_pullup(dev, tm);
+
 			w1_write_8(dev, W1_CONVERT_TEMP);
-			if (!w1_strong_pullup)
-				msleep(tm);
+
+			if (external_power) {
+				mutex_unlock(&dev->mutex);
+
+				sleep_rem = msleep_interruptible(tm);
+				if (sleep_rem != 0)
+					return -EINTR;
+
+				i = mutex_lock_interruptible(&dev->mutex);
+				if (i != 0)
+					return i;
+			} else if (!w1_strong_pullup) {
+				sleep_rem = msleep_interruptible(tm);
+				if (sleep_rem != 0) {
+					mutex_unlock(&dev->mutex);
+					return -EINTR;
+				}
+			}
 
 			if (!w1_reset_select_slave(sl)) {
Acked-by on v1 1/1
#1 lore raw

+gregkh

Quoted 10 lines · Maciej Szmigiero

w1_therm devices can either be bus powered or externally powered.

When device is bus powered during temperature conversion the bus have to be left high to provide necessary power. Some masters also allow strong power-up to be enabled in this case.
Naturally, no communication over bus can occur during that time.

However, if device has external power then there is no such restriction, and host can talk to other devices during temperature conversion.

Quoted 7 lines

There is command which allows us to check how device is powered, this patch uses it to release the bus on externally w1_therm powered devices during temperature conversion.

Also, this changes uninterruptible sleeps there into interruptible ones to avoid long uninterruptible sleep if w1 subsystem happens to grab bus for scan during w1_therm_read().

Patch looks good, but I do not have such hardware to test it. So, if it doesn't break things I'm ok to push it upstream. Greg, please pull it into your tree, thank you.

Quoted 1 line
Signed-off-by Maciej Szmigiero <[email protected]>
Acked-by Evgeniy Polyakov <[email protected]>
Signature · 1 line
	Evgeniy Polyakov