[PATCH 2/3] hwmon: (pmbus) Add documentation for new flags

From: Erik Rosen <erik.rosen@metormote.com>
To: Jean Delvare <jdelvare@suse.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: Erik Rosen <erik.rosen@metormote.com>
Subject: [PATCH 2/3] hwmon: (pmbus) Add documentation for new flags
Date: Wed,  5 May 2021 20:32:47 +0200	[thread overview]
Message-ID: <20210505183248.57082-3-erik.rosen@metormote.com> (raw)
In-Reply-To: <20210505183248.57082-1-erik.rosen@metormote.com>

Add documentation for the new pmbus flags PMBUS_WRITE_PROTECTED and
PMBUS_READ_STATUS_AFTER_FAILED_CHECK

Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
---
 Documentation/hwmon/pmbus-core.rst | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/Documentation/hwmon/pmbus-core.rst b/Documentation/hwmon/pmbus-core.rst
index 73e23ab42cc3..001c64f0f8c0 100644
--- a/Documentation/hwmon/pmbus-core.rst
+++ b/Documentation/hwmon/pmbus-core.rst
@@ -289,9 +289,13 @@ PMBus driver platform data
 ==========================
 
 PMBus platform data is defined in include/linux/pmbus.h. Platform data
-currently only provides a flag field with a single bit used::
+currently only provides a flag field with three bits used::
 
-	#define PMBUS_SKIP_STATUS_CHECK (1 << 0)
+	#define PMBUS_SKIP_STATUS_CHECK  BIT(0)
+
+  #define PMBUS_WRITE_PROTECTED BIT(1)
+
+  #define PMBUS_READ_STATUS_AFTER_FAILED_CHECK  BIT(2)
 
 	struct pmbus_platform_data {
 		u32 flags;              /* Device specific flags */
@@ -315,3 +319,19 @@ status register must be disabled.
 Some i2c controllers do not support single-byte commands (write commands with
 no data, i2c_smbus_write_byte()). With such controllers, clearing the status
 register is impossible, and the PMBUS_SKIP_STATUS_CHECK flag must be set.
+
+PMBUS_WRITE_PROTECTED
+
+Set if the chip is write protected and write protection is not determined
+by the standard WRITE_PROTECT command.
+
+PMBUS_READ_STATUS_AFTER_FAILED_CHECK
+  Read the STATUS register after each failed register 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.
\ No newline at end of file
-- 
2.20.1

