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Commit e76f67b5 authored by Jean Delvare's avatar Jean Delvare Committed by Jean Delvare
Browse files

hwmon: (lm75) Speed up detection 



Make the LM75/LM75A device detection faster:

* Don't read the current temperature value when we don't use it.
* Check for unused bits in the configuration register as soon as we
  have read its value.
* Don't use word reads, not all devices support this, and some which
  don't misbehave when you try.
* Check for cycling register values every 40 register addresses
  instead of every 8, it's 5 times faster and just as efficient.

Some of these improvements come straight from the user-space
sensors-detect script, so both detection routines are in line now.

Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
Cc: Len Sorensen <lsorense@csclub.uwaterloo.ca>
Acked-by: default avatarGuenter Roeck <guenter.roeck@ericsson.com>
parent 05e82fe4

drivers/hwmon/lm75.c

+19 −21
Original line number Diff line number Diff line
@@ -240,7 +240,7 @@ static int lm75_detect(struct i2c_client *new_client, 
{

	struct i2c_adapter *adapter = new_client->adapter;

	int i;

	int cur, conf, hyst, os;

	int conf, hyst, os;

	bool is_lm75a = 0;



	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
@@ -261,8 +261,10 @@ static int lm75_detect(struct i2c_client *new_client, 
	   register 7, and unused registers return 0xff rather than the

	   last read value. */



	cur = i2c_smbus_read_word_data(new_client, 0);

	/* Unused bits */

	conf = i2c_smbus_read_byte_data(new_client, 1);

	if (conf & 0xe0)

		return -ENODEV;



	/* First check for LM75A */

	if (i2c_smbus_read_byte_data(new_client, 7) == LM75A_ID) {
@@ -273,33 +275,29 @@ static int lm75_detect(struct i2c_client *new_client, 
		 || i2c_smbus_read_byte_data(new_client, 6) != 0xff)

			return -ENODEV;

		is_lm75a = 1;

		hyst = i2c_smbus_read_word_data(new_client, 2);

		os = i2c_smbus_read_word_data(new_client, 3);

		hyst = i2c_smbus_read_byte_data(new_client, 2);

		os = i2c_smbus_read_byte_data(new_client, 3);

	} else { /* Traditional style LM75 detection */

		/* Unused addresses */

		hyst = i2c_smbus_read_word_data(new_client, 2);

		if (i2c_smbus_read_word_data(new_client, 4) != hyst

		 || i2c_smbus_read_word_data(new_client, 5) != hyst

		 || i2c_smbus_read_word_data(new_client, 6) != hyst

		 || i2c_smbus_read_word_data(new_client, 7) != hyst)

		hyst = i2c_smbus_read_byte_data(new_client, 2);

		if (i2c_smbus_read_byte_data(new_client, 4) != hyst

		 || i2c_smbus_read_byte_data(new_client, 5) != hyst

		 || i2c_smbus_read_byte_data(new_client, 6) != hyst

		 || i2c_smbus_read_byte_data(new_client, 7) != hyst)

			return -ENODEV;

		os = i2c_smbus_read_word_data(new_client, 3);

		if (i2c_smbus_read_word_data(new_client, 4) != os

		 || i2c_smbus_read_word_data(new_client, 5) != os

		 || i2c_smbus_read_word_data(new_client, 6) != os

		 || i2c_smbus_read_word_data(new_client, 7) != os)

		os = i2c_smbus_read_byte_data(new_client, 3);

		if (i2c_smbus_read_byte_data(new_client, 4) != os

		 || i2c_smbus_read_byte_data(new_client, 5) != os

		 || i2c_smbus_read_byte_data(new_client, 6) != os

		 || i2c_smbus_read_byte_data(new_client, 7) != os)

			return -ENODEV;

	}



	/* Unused bits */

	if (conf & 0xe0)

		return -ENODEV;



	/* Addresses cycling */

	for (i = 8; i < 0xff; i += 8) {

	for (i = 8; i <= 248; i += 40) {

		if (i2c_smbus_read_byte_data(new_client, i + 1) != conf

		 || i2c_smbus_read_word_data(new_client, i + 2) != hyst

		 || i2c_smbus_read_word_data(new_client, i + 3) != os)

		 || i2c_smbus_read_byte_data(new_client, i + 2) != hyst

		 || i2c_smbus_read_byte_data(new_client, i + 3) != os)

			return -ENODEV;

		if (is_lm75a && i2c_smbus_read_byte_data(new_client, i + 7)

				!= LM75A_ID)