[PATCH v3 1/2] hwmon: (pmbus) export pmbus_wait and pmbus_update_ts

[Sanman Pradhan]

Some PMBus devices require strict inter-transaction delays to avoid
NACKs or communication faults. The PMBus core manages this automatically
for standard PMBus accesses via pmbus_wait() and pmbus_update_ts().

However, when a device driver performs raw I2C/SMBus transfers (e.g.,
for long reads or custom commands) that bypass the PMBus core, the core's
timing state machine is unaware of the transaction. This can cause the
next core-mediated PMBus access to violate the device's required delay.

Export pmbus_wait() and pmbus_update_ts() to the PMBUS namespace so
device-specific drivers can explicitly synchronize their raw transfers
with the core's delay management.

Additionally, move the PMBUS_OP_WRITE and PMBUS_OP_PAGE_CHANGE bitmasks
into the drivers/hwmon/pmbus/pmbus.h header so callers can accurately
report the nature of their raw transactions.

Signed-off-by: Sanman Pradhan <psanman@xxxxxxxxxxx>
---
v3:
- No changes to this patch in this version.

v2:
- New patch in the series.
- Export pmbus_wait() and pmbus_update_ts() to the PMBUS namespace.
- Relocate PMBUS_OP_* bitmasks to the subsystem header.
---
 drivers/hwmon/pmbus/pmbus.h      |  9 +++++++++
 drivers/hwmon/pmbus/pmbus_core.c | 13 ++++---------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index 3ddcb742d289..56620ed4ac9c 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -424,6 +424,13 @@ enum vrm_version { vr11 = 0, vr12, vr13, imvp9, amd625mv, nvidia195mv };
 #define PMBUS_REV_12 0x22	/* PMBus revision 1.2 */
 #define PMBUS_REV_13 0x33	/* PMBus revision 1.3 */
 
+/*
+ * 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)
+
 struct pmbus_driver_info {
 	int pages;		/* Total number of pages */
 	u8 phases[PMBUS_PAGES];	/* Number of phases per page */
@@ -555,6 +562,8 @@ int pmbus_update_byte_data(struct i2c_client *client, int page, u8 reg,
 void pmbus_clear_faults(struct i2c_client *client);
 bool pmbus_check_byte_register(struct i2c_client *client, int page, int reg);
 bool pmbus_check_word_register(struct i2c_client *client, int page, int reg);
+void pmbus_wait(struct i2c_client *client);
+void pmbus_update_ts(struct i2c_client *client, int op);
 int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info);
 const struct pmbus_driver_info *pmbus_get_driver_info(struct i2c_client
 						      *client);
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 4d7634ee6148..b150c2ee670a 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -32,13 +32,6 @@
 #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);
 
@@ -173,7 +166,7 @@ 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)
+void pmbus_wait(struct i2c_client *client)
 {
 	struct pmbus_data *data = i2c_get_clientdata(client);
 	s64 delay = ktime_us_delta(data->next_access_backoff, ktime_get());
@@ -181,9 +174,10 @@ static void pmbus_wait(struct i2c_client *client)
 	if (delay > 0)
 		fsleep(delay);
 }
+EXPORT_SYMBOL_NS_GPL(pmbus_wait, "PMBUS");
 
 /* Sets the last operation timestamp for pmbus_wait */
-static void pmbus_update_ts(struct i2c_client *client, int op)
+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;
@@ -197,6 +191,7 @@ static void pmbus_update_ts(struct i2c_client *client, int op)
 	if (delay > 0)
 		data->next_access_backoff = ktime_add_us(ktime_get(), delay);
 }
+EXPORT_SYMBOL_NS_GPL(pmbus_update_ts, "PMBUS");
 
 int pmbus_set_page(struct i2c_client *client, int page, int phase)
 {
-- 
2.34.1