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Message-ID: <20250407201002.1198092-1-william@wkennington.com>
Date: Mon, 7 Apr 2025 13:10:02 -0700
From: "William A. Kennington III" <william@...nnington.com>
To: Jean Delvare <jdelvare@...e.com>,
Guenter Roeck <linux@...ck-us.net>
Cc: linux-hwmon@...r.kernel.org,
linux-kernel@...r.kernel.org,
"William A. Kennington III" <william@...nnington.com>
Subject: [PATCH v5] 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@...nnington.com>
---
V1 -> V2: Simplify how the backoff time is stored and computed
V2 -> V3: Use the BIT macro
V3 -> V4: Move defines up
Move op combos outside update call
Remove unused PMBUS_OP_READ
V4 -> V5: Rebase onto 6.15-rc1
drivers/hwmon/pmbus/pmbus.h | 1 +
drivers/hwmon/pmbus/pmbus_core.c | 69 ++++++++++++++++----------------
2 files changed, 36 insertions(+), 34 deletions(-)
diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index ddb19c9726d6..742dafc44390 100644
--- 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 cfeba2e4c5c3..be6d05def115 100644
--- 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");
--
2.49.0.504.g3bcea36a83-goog
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