hwmon: (pmbus) Add new flag PMBUS_READ_STATUS_AFTER_FAILED_CHECK

Some PMBus chips end up in an undefined state when trying to read an
unsupported register. For such chips, it is necessary to reset the
chip pmbus controller to a known state after a failed register check.
This can be done by reading a known register. By setting this flag the
driver will try to read the STATUS register after each failed
register check. This read may fail, but it will put the chip into a
known state.

Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
Link: https://lore.kernel.org/r/20210507194023.61138-2-erik.rosen@metormote.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index bbd7451..1f7fa53 100644 (file)
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -523,6 +523,8 @@ static bool pmbus_check_register(struct i2c_client *client,
        rv = func(client, page, reg);
        if (rv >= 0 && !(data->flags & PMBUS_SKIP_STATUS_CHECK))
                rv = pmbus_check_status_cml(client);
+       if (rv < 0 && (data->flags & PMBUS_READ_STATUS_AFTER_FAILED_CHECK))
+               data->read_status(client, -1);
        pmbus_clear_fault_page(client, -1);
        return rv >= 0;
 }

diff --git a/include/linux/pmbus.h b/include/linux/pmbus.h
index 12cbbf3..edd7c84 100644 (file)
--- a/include/linux/pmbus.h
+++ b/include/linux/pmbus.h
@@ -43,6 +43,19 @@
  */
 #define PMBUS_NO_CAPABILITY                    BIT(2)
 
+/*
+ * PMBUS_READ_STATUS_AFTER_FAILED_CHECK
+ *
+ * Some PMBus chips end up in an undefined state when trying to read an
+ * unsupported register. For such chips, it is necessary to reset the
+ * chip pmbus controller to a known state after a failed register check.
+ * This can be done by reading a known register. By setting this flag the
+ * driver will try to read the STATUS register after each failed
+ * register check. This read may fail, but it will put the chip in a
+ * known state.
+ */
+#define PMBUS_READ_STATUS_AFTER_FAILED_CHECK   BIT(3)
+
 struct pmbus_platform_data {
        u32 flags;              /* Device specific flags */