From: Lars-Peter Clausen lars@metafoo.de
[ Upstream commit 8d655e65237643c48ada2c131b83679bf1105373 ]
When probing the ucd90320 access to some of the registers randomly fails. Sometimes it NACKs a transfer, sometimes it returns just random data and the PEC check fails.
Experimentation shows that this seems to be triggered by a register access directly back to back with a previous register write. Experimentation also shows that inserting a small delay after register writes makes the issue go away.
Use a similar solution to what the max15301 driver does to solve the same problem. Create a custom set of bus read and write functions that make sure that the delay is added.
Fixes: a470f11c5ba2 ("hwmon: (pmbus/ucd9000) Add support for UCD90320 Power Sequencer") Signed-off-by: Lars-Peter Clausen lars@metafoo.de Link: https://lore.kernel.org/r/20230312160312.2227405-1-lars@metafoo.de Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwmon/pmbus/ucd9000.c | 75 +++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+)
diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c index 75fc770c9e403..3daaf22378322 100644 --- a/drivers/hwmon/pmbus/ucd9000.c +++ b/drivers/hwmon/pmbus/ucd9000.c @@ -7,6 +7,7 @@ */
#include <linux/debugfs.h> +#include <linux/delay.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/of_device.h> @@ -16,6 +17,7 @@ #include <linux/i2c.h> #include <linux/pmbus.h> #include <linux/gpio/driver.h> +#include <linux/timekeeping.h> #include "pmbus.h"
enum chips { ucd9000, ucd90120, ucd90124, ucd90160, ucd90320, ucd9090, @@ -65,6 +67,7 @@ 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)
@@ -73,6 +76,73 @@ struct ucd9000_debugfs_entry { u8 index; };
+/* + * It has been observed that the UCD90320 randomly fails register access when + * doing another access right on the back of a register write. To mitigate this + * make sure that there is a minimum delay between a write access and the + * following access. The 250us is based on experimental data. At a delay of + * 200us the issue seems to go away. Add a bit of extra margin to allow for + * system to system differences. + */ +#define UCD90320_WAIT_DELAY_US 250 + +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; @@ -598,6 +668,11 @@ static int ucd9000_probe(struct i2c_client *client) info->read_byte_data = ucd9000_read_byte_data; 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; }
ucd9000_probe_gpio(client, mid, data);