linux-kernel - [PATCH v2 1/2] hwmon: (pmbus) Add a PMBUS_NO

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Date:   Tue, 22 Dec 2020 09:26:39 -0600
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-hwmon@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jdelvare@...e.com,
        linux@...ck-us.net, eajames@...ux.ibm.com, bjwyman@...il.com
Subject: [PATCH v2 1/2] hwmon: (pmbus) Add a PMBUS_NO_CAPABILITY platform data flag

Some PMBus chips don't respond with valid data when reading the
CAPABILITY register. Add a flag that device drivers can set so
that the PMBus core driver doesn't use CAPABILITY to determine it's
behavior.

Signed-off-by: Eddie James <eajames@...ux.ibm.com>
---
 drivers/hwmon/pmbus/pmbus_core.c | 8 +++++---
 include/linux/pmbus.h            | 9 +++++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 192442b3b7a2..906c9fec9cce 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2204,9 +2204,11 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 	}
 
 	/* Enable PEC if the controller supports it */
-	ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
-	if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
-		client->flags |= I2C_CLIENT_PEC;
+	if (!(data->flags & PMBUS_NO_CAPABILITY)) {
+		ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
+		if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
+			client->flags |= I2C_CLIENT_PEC;
+	}
 
 	/*
 	 * Check if the chip is write protected. If it is, we can not clear
diff --git a/include/linux/pmbus.h b/include/linux/pmbus.h
index 1ea5bae708a1..12cbbf305969 100644
--- a/include/linux/pmbus.h
+++ b/include/linux/pmbus.h
@@ -34,6 +34,15 @@
  */
 #define PMBUS_WRITE_PROTECTED	BIT(1)
 
+/*
+ * PMBUS_NO_CAPABILITY
+ *
+ * Some PMBus chips don't respond with valid data when reading the CAPABILITY
+ * register. For such chips, this flag should be set so that the PMBus core
+ * driver doesn't use CAPABILITY to determine it's behavior.
+ */
+#define PMBUS_NO_CAPABILITY			BIT(2)
+
 struct pmbus_platform_data {
 	u32 flags;		/* Device specific flags */
 
-- 
2.27.0