hwmon: (pmbus) Introduce page_change_delay

We have some buggy pmbus devices that require a delay after performing a
page change operation before trying to issue more commands to the
device.

This allows for a configurable delay after page changes, but not
affecting other read or write operations.

This makes a slight behavioral tweak to the existing delay logic, where
it considers the longest of delays between operations, instead of always
chosing the write delay over the access delay.

Signed-off-by: William A. Kennington III <william@wkennington.com>
Link: https://lore.kernel.org/r/20250407201002.1198092-1-william@wkennington.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index ddb19c9726d62416244f83603b92d81d82e64891..742dafc443903183d738e28b68fcf438ee0c922a 100644 (file)
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -482,6 +482,7 @@ struct pmbus_driver_info {
         */
        int access_delay;               /* in microseconds */
        int write_delay;                /* in microseconds */
+       int page_change_delay;          /* in microseconds */
 };
 
 /* Regulator ops */

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index cfeba2e4c5c3f2d53f8af8ad71b83f399778d567..be6d05def1152b04336c5773ba3c006d9b454a73 100644 (file)
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -32,6 +32,13 @@
 #define PMBUS_ATTR_ALLOC_SIZE  32
 #define PMBUS_NAME_SIZE                24
 
+/*
+ * The type of operation used for picking the delay between
+ * successive pmbus operations.
+ */
+#define PMBUS_OP_WRITE         BIT(0)
+#define PMBUS_OP_PAGE_CHANGE   BIT(1)
+
 static int wp = -1;
 module_param(wp, int, 0444);
 
@@ -113,8 +120,8 @@ 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 */
+
+       ktime_t next_access_backoff;    /* Wait until at least this time */
 };
 
 struct pmbus_debugfs_entry {
@@ -169,32 +176,26 @@ EXPORT_SYMBOL_NS_GPL(pmbus_set_update, "PMBUS");
 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;
+       s64 delay = ktime_us_delta(data->next_access_backoff, ktime_get());
 
-       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);
-       }
+       if (delay > 0)
+               fsleep(delay);
 }
 
-/* Sets the last accessed timestamp for pmbus_wait */
-static void pmbus_update_ts(struct i2c_client *client, bool write_op)
+/* Sets the last operation timestamp for pmbus_wait */
+static void pmbus_update_ts(struct i2c_client *client, int op)
 {
        struct pmbus_data *data = i2c_get_clientdata(client);
        const struct pmbus_driver_info *info = data->info;
+       int delay = info->access_delay;
+
+       if (op & PMBUS_OP_WRITE)
+               delay = max(delay, info->write_delay);
+       if (op & PMBUS_OP_PAGE_CHANGE)
+               delay = max(delay, info->page_change_delay);
 
-       if (info->access_delay)
-               data->access_time = ktime_get();
-       else if (info->write_delay && write_op)
-               data->write_time = ktime_get();
+       if (delay > 0)
+               data->next_access_backoff = ktime_add_us(ktime_get(), delay);
 }
 
 int pmbus_set_page(struct i2c_client *client, int page, int phase)
@@ -209,13 +210,13 @@ int pmbus_set_page(struct i2c_client *client, int page, int phase)
            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);
+               pmbus_update_ts(client, PMBUS_OP_WRITE | PMBUS_OP_PAGE_CHANGE);
                if (rv < 0)
                        return rv;
 
                pmbus_wait(client);
                rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
-               pmbus_update_ts(client, false);
+               pmbus_update_ts(client, 0);
                if (rv < 0)
                        return rv;
 
@@ -229,7 +230,7 @@ int pmbus_set_page(struct i2c_client *client, int page, int phase)
                pmbus_wait(client);
                rv = i2c_smbus_write_byte_data(client, PMBUS_PHASE,
                                               phase);
-               pmbus_update_ts(client, true);
+               pmbus_update_ts(client, PMBUS_OP_WRITE);
                if (rv)
                        return rv;
        }
@@ -249,7 +250,7 @@ int pmbus_write_byte(struct i2c_client *client, int page, u8 value)
 
        pmbus_wait(client);
        rv = i2c_smbus_write_byte(client, value);
-       pmbus_update_ts(client, true);
+       pmbus_update_ts(client, PMBUS_OP_WRITE);
 
        return rv;
 }
@@ -284,7 +285,7 @@ int pmbus_write_word_data(struct i2c_client *client, int page, u8 reg,
 
        pmbus_wait(client);
        rv = i2c_smbus_write_word_data(client, reg, word);
-       pmbus_update_ts(client, true);
+       pmbus_update_ts(client, PMBUS_OP_WRITE);
 
        return rv;
 }
@@ -405,7 +406,7 @@ int pmbus_read_word_data(struct i2c_client *client, int page, int phase, u8 reg)
 
        pmbus_wait(client);
        rv = i2c_smbus_read_word_data(client, reg);
-       pmbus_update_ts(client, false);
+       pmbus_update_ts(client, 0);
 
        return rv;
 }
@@ -468,7 +469,7 @@ int pmbus_read_byte_data(struct i2c_client *client, int page, u8 reg)
 
        pmbus_wait(client);
        rv = i2c_smbus_read_byte_data(client, reg);
-       pmbus_update_ts(client, false);
+       pmbus_update_ts(client, 0);
 
        return rv;
 }
@@ -484,7 +485,7 @@ int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg, u8 value)
 
        pmbus_wait(client);
        rv = i2c_smbus_write_byte_data(client, reg, value);
-       pmbus_update_ts(client, true);
+       pmbus_update_ts(client, PMBUS_OP_WRITE);
 
        return rv;
 }
@@ -520,7 +521,7 @@ static int pmbus_read_block_data(struct i2c_client *client, int page, u8 reg,
 
        pmbus_wait(client);
        rv = i2c_smbus_read_block_data(client, reg, data_buf);
-       pmbus_update_ts(client, false);
+       pmbus_update_ts(client, 0);
 
        return rv;
 }
@@ -2524,7 +2525,7 @@ static int pmbus_read_coefficients(struct i2c_client *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);
+       pmbus_update_ts(client, PMBUS_OP_WRITE);
 
        if (rv < 0)
                return rv;
@@ -2728,7 +2729,7 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
        if (!(data->flags & PMBUS_NO_CAPABILITY)) {
                pmbus_wait(client);
                ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
-               pmbus_update_ts(client, false);
+               pmbus_update_ts(client, 0);
 
                if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) {
                        if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_PEC))
@@ -2744,13 +2745,13 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
        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);
+       pmbus_update_ts(client, 0);
 
        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);
+               pmbus_update_ts(client, 0);
 
                if (ret < 0 || ret == 0xff) {
                        dev_err(dev, "PMBus status register not found\n");