[PATCH v3 1/5] hwmon: pmbus: Implement generic bus access delay

[PATCH v3 1/5] hwmon: pmbus: Implement generic bus access delay

[Patrick Rudolph]

Some drivers, like the max15301 or zl6100, are intentionally delaying
SMBus communications, to prevent transmission errors. As this is necessary
on additional PMBus compatible devices, implement a generic delay mechanism
in the pmbus core.

Introduces two delay settings in the pmbus_driver_info struct, one applies
to every SMBus transaction and the other is for write transaction only.
Once set by the driver the SMBus traffic, using the generic pmbus access
helpers, is automatically delayed when necessary.

The two settings are:
access_delay:
  - Unit in microseconds
  - Stores the accessed timestamp after every SMBus access
  - Delays when necessary before the next SMBus access

write_delay:
  - Unit in microseconds
  - Stores the written timestamp after a write SMBus access
  - Delays when necessary before the next SMBus access

This allows to drop the custom delay code from the drivers and easily
introduce this feature in additional pmbus drivers.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
Changelog v2:
- Rename pmbus_optional_wait()
- Drop inline keyword
- Use fsleep over usleep

Changelog v3:
- Added changelog

 drivers/hwmon/pmbus/pmbus.h      | 10 ++++
 drivers/hwmon/pmbus/pmbus_core.c | 92 +++++++++++++++++++++++++++++---
 2 files changed, 96 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index fb442fae7b3e..5d5dc774187b 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -466,6 +466,16 @@ struct pmbus_driver_info {
 
 	/* custom attributes */
 	const struct attribute_group **groups;
+
+	/*
+	 * Some chips need a little delay between SMBus communication. When
+	 * set, the generic PMBus helper functions will wait if necessary
+	 * to meet this requirement. The access delay is honored after
+	 * every SMBus operation. The write delay is only honored after
+	 * SMBus write operations.
+	 */
+	int access_delay;		/* in microseconds */
+	int write_delay;		/* in microseconds */
 };
 
 /* Regulator ops */
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index cb4c65a7f288..0ea6fe7eb17c 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/debugfs.h>
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/math64.h>
 #include <linux/module.h>
@@ -108,6 +109,8 @@ struct pmbus_data {
 
 	int vout_low[PMBUS_PAGES];	/* voltage low margin */
 	int vout_high[PMBUS_PAGES];	/* voltage high margin */
+	ktime_t write_time;		/* Last SMBUS write timestamp */
+	ktime_t access_time;		/* Last SMBUS access timestamp */
 };
 
 struct pmbus_debugfs_entry {
@@ -158,6 +161,39 @@ void pmbus_set_update(struct i2c_client *client, u8 reg, bool update)
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_set_update, PMBUS);
 
+/* Some chips need a delay between accesses. */
+static void pmbus_wait(struct i2c_client *client)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+	const struct pmbus_driver_info *info = data->info;
+	s64 delta;
+
+	if (info->access_delay) {
+		delta = ktime_us_delta(ktime_get(), data->access_time);
+
+		if (delta < info->access_delay)
+			fsleep(info->access_delay - delta);
+	} else if (info->write_delay) {
+		delta = ktime_us_delta(ktime_get(), data->write_time);
+
+		if (delta < info->write_delay)
+			fsleep(info->write_delay - delta);
+	}
+}
+
+/* Sets the last accessed timestamp for pmbus_wait */
+static void pmbus_update_ts(struct i2c_client *client, bool write_op)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+	const struct pmbus_driver_info *info = data->info;
+
+	if (info->access_delay) {
+		data->access_time = ktime_get();
+	} else if (info->write_delay && write_op) {
+		data->write_time = ktime_get();
+	}
+}
+
 int pmbus_set_page(struct i2c_client *client, int page, int phase)
 {
 	struct pmbus_data *data = i2c_get_clientdata(client);
@@ -168,11 +204,15 @@ int pmbus_set_page(struct i2c_client *client, int page, int phase)
 
 	if (!(data->info->func[page] & PMBUS_PAGE_VIRTUAL) &&
 	    data->info->pages > 1 && page != data->currpage) {
+		pmbus_wait(client);
 		rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
+		pmbus_update_ts(client, true);
 		if (rv < 0)
 			return rv;
 
+		pmbus_wait(client);
 		rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
+		pmbus_update_ts(client, false);
 		if (rv < 0)
 			return rv;
 
@@ -183,8 +223,10 @@ int pmbus_set_page(struct i2c_client *client, int page, int phase)
 
 	if (data->info->phases[page] && data->currphase != phase &&
 	    !(data->info->func[page] & PMBUS_PHASE_VIRTUAL)) {
+		pmbus_wait(client);
 		rv = i2c_smbus_write_byte_data(client, PMBUS_PHASE,
 					       phase);
+		pmbus_update_ts(client, true);
 		if (rv)
 			return rv;
 	}
@@ -202,7 +244,11 @@ int pmbus_write_byte(struct i2c_client *client, int page, u8 value)
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_write_byte(client, value);
+	pmbus_wait(client);
+	rv = i2c_smbus_write_byte(client, value);
+	pmbus_update_ts(client, true);
+
+	return rv;
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_write_byte, PMBUS);
 
@@ -233,7 +279,11 @@ int pmbus_write_word_data(struct i2c_client *client, int page, u8 reg,
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_write_word_data(client, reg, word);
+	pmbus_wait(client);
+	rv = i2c_smbus_write_word_data(client, reg, word);
+	pmbus_update_ts(client, true);
+
+	return rv;
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_write_word_data, PMBUS);
 
@@ -351,7 +401,11 @@ int pmbus_read_word_data(struct i2c_client *client, int page, int phase, u8 reg)
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_read_word_data(client, reg);
+	pmbus_wait(client);
+	rv = i2c_smbus_read_word_data(client, reg);
+	pmbus_update_ts(client, false);
+
+	return rv;
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_read_word_data, PMBUS);
 
@@ -410,7 +464,11 @@ int pmbus_read_byte_data(struct i2c_client *client, int page, u8 reg)
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_read_byte_data(client, reg);
+	pmbus_wait(client);
+	rv = i2c_smbus_read_byte_data(client, reg);
+	pmbus_update_ts(client, false);
+
+	return rv;
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_read_byte_data, PMBUS);
 
@@ -422,7 +480,11 @@ int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg, u8 value)
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_write_byte_data(client, reg, value);
+	pmbus_wait(client);
+	rv = i2c_smbus_write_byte_data(client, reg, value);
+	pmbus_update_ts(client, true);
+
+	return rv;
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_write_byte_data, PMBUS);
 
@@ -454,7 +516,11 @@ static int pmbus_read_block_data(struct i2c_client *client, int page, u8 reg,
 	if (rv < 0)
 		return rv;
 
-	return i2c_smbus_read_block_data(client, reg, data_buf);
+	pmbus_wait(client);
+	rv = i2c_smbus_read_block_data(client, reg, data_buf);
+	pmbus_update_ts(client, false);
+
+	return rv;
 }
 
 static struct pmbus_sensor *pmbus_find_sensor(struct pmbus_data *data, int page,
@@ -2450,9 +2516,11 @@ static int pmbus_read_coefficients(struct i2c_client *client,
 	data.block[1] = attr->reg;
 	data.block[2] = 0x01;
 
+	pmbus_wait(client);
 	rv = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
 			    I2C_SMBUS_WRITE, PMBUS_COEFFICIENTS,
 			    I2C_SMBUS_BLOCK_PROC_CALL, &data);
+	pmbus_update_ts(client, true);
 
 	if (rv < 0)
 		return rv;
@@ -2604,7 +2672,10 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 
 	/* Enable PEC if the controller and bus supports it */
 	if (!(data->flags & PMBUS_NO_CAPABILITY)) {
+		pmbus_wait(client);
 		ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
+		pmbus_update_ts(client, false);
+
 		if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) {
 			if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_PEC))
 				client->flags |= I2C_CLIENT_PEC;
@@ -2617,10 +2688,16 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 	 * Bail out if both registers are not supported.
 	 */
 	data->read_status = pmbus_read_status_word;
+	pmbus_wait(client);
 	ret = i2c_smbus_read_word_data(client, PMBUS_STATUS_WORD);
+	pmbus_update_ts(client, false);
+
 	if (ret < 0 || ret == 0xffff) {
 		data->read_status = pmbus_read_status_byte;
+		pmbus_wait(client);
 		ret = i2c_smbus_read_byte_data(client, PMBUS_STATUS_BYTE);
+		pmbus_update_ts(client, false);
+
 		if (ret < 0 || ret == 0xff) {
 			dev_err(dev, "PMBus status register not found\n");
 			return -ENODEV;
@@ -2635,7 +2712,10 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 	 * limit registers need to be disabled.
 	 */
 	if (!(data->flags & PMBUS_NO_WRITE_PROTECT)) {
+		pmbus_wait(client);
 		ret = i2c_smbus_read_byte_data(client, PMBUS_WRITE_PROTECT);
+		pmbus_update_ts(client, false);
+
 		if (ret > 0 && (ret & PB_WP_ANY))
 			data->flags |= PMBUS_WRITE_PROTECTED | PMBUS_SKIP_STATUS_CHECK;
 	}
-- 
2.45.2

[PATCH v3 2/5] hwmon: pmbus: max15301: Use generic code

[Patrick Rudolph]

Use the generic pmbus bus access delay.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
Changelog v2:
- No change

Changelog v3:
- Added changelog

 drivers/hwmon/pmbus/max15301.c | 92 +---------------------------------
 1 file changed, 1 insertion(+), 91 deletions(-)

diff --git a/drivers/hwmon/pmbus/max15301.c b/drivers/hwmon/pmbus/max15301.c
index 986404fe6a31..f5367a7bc0f5 100644
--- a/drivers/hwmon/pmbus/max15301.c
+++ b/drivers/hwmon/pmbus/max15301.c
@@ -31,8 +31,6 @@ MODULE_DEVICE_TABLE(i2c, max15301_id);
 
 struct max15301_data {
 	int id;
-	ktime_t access;		/* Chip access time */
-	int delay;		/* Delay between chip accesses in us */
 	struct pmbus_driver_info info;
 };
 
@@ -55,89 +53,6 @@ static struct max15301_data max15301_data = {
 	}
 };
 
-/* This chip needs a delay between accesses */
-static inline void max15301_wait(const struct max15301_data *data)
-{
-	if (data->delay) {
-		s64 delta = ktime_us_delta(ktime_get(), data->access);
-
-		if (delta < data->delay)
-			udelay(data->delay - delta);
-	}
-}
-
-static int max15301_read_word_data(struct i2c_client *client, int page,
-				   int phase, int reg)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct max15301_data *data = to_max15301_data(info);
-	int ret;
-
-	if (page > 0)
-		return -ENXIO;
-
-	if (reg >= PMBUS_VIRT_BASE)
-		return -ENXIO;
-
-	max15301_wait(data);
-	ret = pmbus_read_word_data(client, page, phase, reg);
-	data->access = ktime_get();
-
-	return ret;
-}
-
-static int max15301_read_byte_data(struct i2c_client *client, int page, int reg)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct max15301_data *data = to_max15301_data(info);
-	int ret;
-
-	if (page > 0)
-		return -ENXIO;
-
-	max15301_wait(data);
-	ret = pmbus_read_byte_data(client, page, reg);
-	data->access = ktime_get();
-
-	return ret;
-}
-
-static int max15301_write_word_data(struct i2c_client *client, int page, int reg,
-				    u16 word)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct max15301_data *data = to_max15301_data(info);
-	int ret;
-
-	if (page > 0)
-		return -ENXIO;
-
-	if (reg >= PMBUS_VIRT_BASE)
-		return -ENXIO;
-
-	max15301_wait(data);
-	ret = pmbus_write_word_data(client, page, reg, word);
-	data->access = ktime_get();
-
-	return ret;
-}
-
-static int max15301_write_byte(struct i2c_client *client, int page, u8 value)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct max15301_data *data = to_max15301_data(info);
-	int ret;
-
-	if (page > 0)
-		return -ENXIO;
-
-	max15301_wait(data);
-	ret = pmbus_write_byte(client, page, value);
-	data->access = ktime_get();
-
-	return ret;
-}
-
 static int max15301_probe(struct i2c_client *client)
 {
 	int status;
@@ -164,12 +79,7 @@ static int max15301_probe(struct i2c_client *client)
 		return -ENODEV;
 	}
 
-	max15301_data.delay = delay;
-
-	info->read_byte_data = max15301_read_byte_data;
-	info->read_word_data = max15301_read_word_data;
-	info->write_byte = max15301_write_byte;
-	info->write_word_data = max15301_write_word_data;
+	info->access_delay = delay;
 
 	return pmbus_do_probe(client, info);
 }
-- 
2.45.2

[PATCH v3 3/5] hwmon: pmbus: ucd9000: Use generic code

[Patrick Rudolph]

Use generic pmbus bus write access delay.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
Changelog v2:
- No change

Changelog v3:
- Added changelog

 drivers/hwmon/pmbus/ucd9000.c | 64 ++---------------------------------
 1 file changed, 2 insertions(+), 62 deletions(-)

diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
index d817c719b90b..5d3d1773bf52 100644
--- a/drivers/hwmon/pmbus/ucd9000.c
+++ b/drivers/hwmon/pmbus/ucd9000.c
@@ -67,7 +67,6 @@ struct ucd9000_data {
 	struct gpio_chip gpio;
 #endif
 	struct dentry *debugfs;
-	ktime_t write_time;
 };
 #define to_ucd9000_data(_info) container_of(_info, struct ucd9000_data, info)
 
@@ -86,63 +85,6 @@ struct ucd9000_debugfs_entry {
  */
 #define UCD90320_WAIT_DELAY_US 500
 
-static inline void ucd90320_wait(const struct ucd9000_data *data)
-{
-	s64 delta = ktime_us_delta(ktime_get(), data->write_time);
-
-	if (delta < UCD90320_WAIT_DELAY_US)
-		udelay(UCD90320_WAIT_DELAY_US - delta);
-}
-
-static int ucd90320_read_word_data(struct i2c_client *client, int page,
-				   int phase, int reg)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct ucd9000_data *data = to_ucd9000_data(info);
-
-	if (reg >= PMBUS_VIRT_BASE)
-		return -ENXIO;
-
-	ucd90320_wait(data);
-	return pmbus_read_word_data(client, page, phase, reg);
-}
-
-static int ucd90320_read_byte_data(struct i2c_client *client, int page, int reg)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct ucd9000_data *data = to_ucd9000_data(info);
-
-	ucd90320_wait(data);
-	return pmbus_read_byte_data(client, page, reg);
-}
-
-static int ucd90320_write_word_data(struct i2c_client *client, int page,
-				    int reg, u16 word)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct ucd9000_data *data = to_ucd9000_data(info);
-	int ret;
-
-	ucd90320_wait(data);
-	ret = pmbus_write_word_data(client, page, reg, word);
-	data->write_time = ktime_get();
-
-	return ret;
-}
-
-static int ucd90320_write_byte(struct i2c_client *client, int page, u8 value)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct ucd9000_data *data = to_ucd9000_data(info);
-	int ret;
-
-	ucd90320_wait(data);
-	ret = pmbus_write_byte(client, page, value);
-	data->write_time = ktime_get();
-
-	return ret;
-}
-
 static int ucd9000_get_fan_config(struct i2c_client *client, int fan)
 {
 	int fan_config = 0;
@@ -667,10 +609,8 @@ static int ucd9000_probe(struct i2c_client *client)
 		info->func[0] |= PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12
 		  | PMBUS_HAVE_FAN34 | PMBUS_HAVE_STATUS_FAN34;
 	} else if (mid->driver_data == ucd90320) {
-		info->read_byte_data = ucd90320_read_byte_data;
-		info->read_word_data = ucd90320_read_word_data;
-		info->write_byte = ucd90320_write_byte;
-		info->write_word_data = ucd90320_write_word_data;
+		/* Delay SMBus operations after a write */
+		info->write_delay = UCD90320_WAIT_DELAY_US;
 	}
 
 	ucd9000_probe_gpio(client, mid, data);
-- 
2.45.2

[PATCH v3 4/5] hwmon: pmbus: zl6100: Use generic code

[Patrick Rudolph]

Use generic pmbus bus access delay.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
Changelog v2:
- Drop now unused variables to make it compile

Changelog v3:
- Added changelog

 drivers/hwmon/pmbus/zl6100.c | 66 +++++-------------------------------
 1 file changed, 8 insertions(+), 58 deletions(-)

diff --git a/drivers/hwmon/pmbus/zl6100.c b/drivers/hwmon/pmbus/zl6100.c
index 83458df0d0cf..7920a16203e1 100644
--- a/drivers/hwmon/pmbus/zl6100.c
+++ b/drivers/hwmon/pmbus/zl6100.c
@@ -22,8 +22,6 @@ enum chips { zl2004, zl2005, zl2006, zl2008, zl2105, zl2106, zl6100, zl6105,
 
 struct zl6100_data {
 	int id;
-	ktime_t access;		/* chip access time */
-	int delay;		/* Delay between chip accesses in uS */
 	struct pmbus_driver_info info;
 };
 
@@ -122,16 +120,6 @@ static u16 zl6100_d2l(long val)
 	return (mantissa & 0x7ff) | ((exponent << 11) & 0xf800);
 }
 
-/* Some chips need a delay between accesses */
-static inline void zl6100_wait(const struct zl6100_data *data)
-{
-	if (data->delay) {
-		s64 delta = ktime_us_delta(ktime_get(), data->access);
-		if (delta < data->delay)
-			udelay(data->delay - delta);
-	}
-}
-
 static int zl6100_read_word_data(struct i2c_client *client, int page,
 				 int phase, int reg)
 {
@@ -174,9 +162,7 @@ static int zl6100_read_word_data(struct i2c_client *client, int page,
 		break;
 	}
 
-	zl6100_wait(data);
 	ret = pmbus_read_word_data(client, page, phase, vreg);
-	data->access = ktime_get();
 	if (ret < 0)
 		return ret;
 
@@ -195,14 +181,11 @@ static int zl6100_read_word_data(struct i2c_client *client, int page,
 static int zl6100_read_byte_data(struct i2c_client *client, int page, int reg)
 {
 	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct zl6100_data *data = to_zl6100_data(info);
 	int ret, status;
 
 	if (page >= info->pages)
 		return -ENXIO;
 
-	zl6100_wait(data);
-
 	switch (reg) {
 	case PMBUS_VIRT_STATUS_VMON:
 		ret = pmbus_read_byte_data(client, 0,
@@ -225,7 +208,6 @@ static int zl6100_read_byte_data(struct i2c_client *client, int page, int reg)
 		ret = pmbus_read_byte_data(client, page, reg);
 		break;
 	}
-	data->access = ktime_get();
 
 	return ret;
 }
@@ -234,8 +216,7 @@ static int zl6100_write_word_data(struct i2c_client *client, int page, int reg,
 				  u16 word)
 {
 	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct zl6100_data *data = to_zl6100_data(info);
-	int ret, vreg;
+	int vreg;
 
 	if (page >= info->pages)
 		return -ENXIO;
@@ -265,27 +246,7 @@ static int zl6100_write_word_data(struct i2c_client *client, int page, int reg,
 		vreg = reg;
 	}
 
-	zl6100_wait(data);
-	ret = pmbus_write_word_data(client, page, vreg, word);
-	data->access = ktime_get();
-
-	return ret;
-}
-
-static int zl6100_write_byte(struct i2c_client *client, int page, u8 value)
-{
-	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
-	struct zl6100_data *data = to_zl6100_data(info);
-	int ret;
-
-	if (page >= info->pages)
-		return -ENXIO;
-
-	zl6100_wait(data);
-	ret = pmbus_write_byte(client, page, value);
-	data->access = ktime_get();
-
-	return ret;
+	return pmbus_write_word_data(client, page, vreg, word);
 }
 
 static const struct i2c_device_id zl6100_id[] = {
@@ -363,14 +324,7 @@ static int zl6100_probe(struct i2c_client *client)
 	 * supported chips are known to require a wait time between I2C
 	 * accesses.
 	 */
-	data->delay = delay;
-
-	/*
-	 * Since there was a direct I2C device access above, wait before
-	 * accessing the chip again.
-	 */
-	data->access = ktime_get();
-	zl6100_wait(data);
+	udelay(delay);
 
 	info = &data->info;
 
@@ -404,8 +358,7 @@ static int zl6100_probe(struct i2c_client *client)
 		if (ret < 0)
 			return ret;
 
-		data->access = ktime_get();
-		zl6100_wait(data);
+		udelay(delay);
 
 		if (ret & ZL8802_MFR_PHASES_MASK)
 			info->func[1] |= PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT;
@@ -418,8 +371,7 @@ static int zl6100_probe(struct i2c_client *client)
 			if (ret < 0)
 				return ret;
 
-			data->access = ktime_get();
-			zl6100_wait(data);
+			udelay(delay);
 
 			ret = i2c_smbus_read_word_data(client, ZL8802_MFR_USER_CONFIG);
 			if (ret < 0)
@@ -428,8 +380,7 @@ static int zl6100_probe(struct i2c_client *client)
 			if (ret & ZL8802_MFR_XTEMP_ENABLE_2)
 				info->func[i] |= PMBUS_HAVE_TEMP2;
 
-			data->access = ktime_get();
-			zl6100_wait(data);
+			udelay(delay);
 		}
 		ret = i2c_smbus_read_word_data(client, ZL8802_MFR_USER_GLOBAL_CONFIG);
 		if (ret < 0)
@@ -446,13 +397,12 @@ static int zl6100_probe(struct i2c_client *client)
 			info->func[0] |= PMBUS_HAVE_TEMP2;
 	}
 
-	data->access = ktime_get();
-	zl6100_wait(data);
+	udelay(delay);
 
+	info->access_delay = delay;
 	info->read_word_data = zl6100_read_word_data;
 	info->read_byte_data = zl6100_read_byte_data;
 	info->write_word_data = zl6100_write_word_data;
-	info->write_byte = zl6100_write_byte;
 
 	return pmbus_do_probe(client, info);
 }
-- 
2.45.2

[PATCH v3 5/5] hwmon: pmbus: pli12096bc: Add write delay

[Patrick Rudolph]

Tests on PLI12096bc showed that sometimes a small delay is necessary
after a write operation before a new operation can be processed.
If not respected the device will probably NACK the data phase of
the SMBus transaction. Tests showed that the probability to observe
transaction errors can be raised by either reading sensor data or
toggling the regulator enable.

Further tests showed that 250 microseconds, as used previously for
the CLEAR_FAULTS workaround, is sufficient.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
Changelog v2:
- No change

Changelog v3:
- Added changelog

 drivers/hwmon/pmbus/pli1209bc.c | 26 +-------------------------
 1 file changed, 1 insertion(+), 25 deletions(-)

diff --git a/drivers/hwmon/pmbus/pli1209bc.c b/drivers/hwmon/pmbus/pli1209bc.c
index 2c6c9ec2a652..178e0cdb7887 100644
--- a/drivers/hwmon/pmbus/pli1209bc.c
+++ b/drivers/hwmon/pmbus/pli1209bc.c
@@ -54,30 +54,6 @@ static int pli1209bc_read_word_data(struct i2c_client *client, int page,
 	}
 }
 
-static int pli1209bc_write_byte(struct i2c_client *client, int page, u8 reg)
-{
-	int ret;
-
-	switch (reg) {
-	case PMBUS_CLEAR_FAULTS:
-		ret = pmbus_write_byte(client, page, reg);
-		/*
-		 * PLI1209 takes 230 usec to execute the CLEAR_FAULTS command.
-		 * During that time it's busy and NACKs all requests on the
-		 * SMBUS interface. It also NACKs reads on PMBUS_STATUS_BYTE
-		 * making it impossible to poll the BUSY flag.
-		 *
-		 * Just wait for not BUSY unconditionally.
-		 */
-		usleep_range(250, 300);
-		break;
-	default:
-		ret = -ENODATA;
-		break;
-	}
-	return ret;
-}
-
 #if IS_ENABLED(CONFIG_SENSORS_PLI1209BC_REGULATOR)
 static const struct regulator_desc pli1209bc_reg_desc = {
 	.name = "vout2",
@@ -127,7 +103,7 @@ static struct pmbus_driver_info pli1209bc_info = {
 	    | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
 	    | PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_INPUT,
 	.read_word_data = pli1209bc_read_word_data,
-	.write_byte = pli1209bc_write_byte,
+	.write_delay = 250,
 #if IS_ENABLED(CONFIG_SENSORS_PLI1209BC_REGULATOR)
 	.num_regulators = 1,
 	.reg_desc = &pli1209bc_reg_desc,
-- 
2.45.2

Re: [PATCH v3 1/5] hwmon: pmbus: Implement generic bus access delay

[Guenter Roeck]

On 9/2/24 00:53, Patrick Rudolph wrote:
> Some drivers, like the max15301 or zl6100, are intentionally delaying
> SMBus communications, to prevent transmission errors. As this is necessary
> on additional PMBus compatible devices, implement a generic delay mechanism
> in the pmbus core.
> 
> Introduces two delay settings in the pmbus_driver_info struct, one applies
> to every SMBus transaction and the other is for write transaction only.
> Once set by the driver the SMBus traffic, using the generic pmbus access
> helpers, is automatically delayed when necessary.
> 
> The two settings are:
> access_delay:
>    - Unit in microseconds
>    - Stores the accessed timestamp after every SMBus access
>    - Delays when necessary before the next SMBus access
> 
> write_delay:
>    - Unit in microseconds
>    - Stores the written timestamp after a write SMBus access
>    - Delays when necessary before the next SMBus access
> 
> This allows to drop the custom delay code from the drivers and easily
> introduce this feature in additional pmbus drivers.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>

Series applied.

Thanks,
Guenter