Patch "hwmon: (ucd90320) Add minimum delay between bus accesses" has been added to the 5.10-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This is a note to let you know that I've just added the patch titled

    hwmon: (ucd90320) Add minimum delay between bus accesses

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hwmon-ucd90320-add-minimum-delay-between-bus-accesse.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 01c8d3897e161ee53bcc51fd7f68ff9888c33162
Author: Lars-Peter Clausen <lars@xxxxxxxxxx>
Date:   Sun Mar 12 09:03:12 2023 -0700

    hwmon: (ucd90320) Add minimum delay between bus accesses
    
    [ 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@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230312160312.2227405-1-lars@xxxxxxxxxx
    Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
index f8017993e2b4d..9e26cc084a176 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);



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux