From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Vishnu Razdan <vrazdan@openai.com>,
	Guenter Roeck <linux@roeck-us.net>
Subject: [PATCH 6.12 0873/1102] hwmon: (pmbus) Clear generic status alarms with CLEAR_FAULTS
Date: Thu, 17 Sep 2026 16:13:36 +0100
Message-ID: <20260917151602.478079854@linuxfoundation.org>
In-Reply-To: <20260917151539.408551884@linuxfoundation.org>
References: <20260917151539.408551884@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vishnu Razdan <vrazdan@openai.com>

commit 6d760f8b41aed74de4402440e4db663d261478bd upstream.

Some hwmon alarms fall back to STATUS_WORD summary bits when no
individual limit alarm is available. On PMBus 1.2 and newer devices,
pmbus_get_boolean() acknowledges these alarms with the same byte-data
write used for detailed status registers. For example, PB_STATUS_INPUT
is 0x2000, so it is truncated to zero when passed to
_pmbus_write_byte_data(). The resulting write cannot acknowledge the
input alarm.

PMBus 1.3 Part II, sections 10.2.4 and 10.2.5, excludes ordinary
STATUS_BYTE and STATUS_WORD summary bits from individual clearing.
Their summary bits clear when the underlying status bits clear, so
changing this to a word-data write would not fix the generic input
alarm either.

Use the existing page CLEAR_FAULTS path for generic STATUS_WORD
alarms, including devices whose status accessor uses STATUS_BYTE.
Keep individual byte writes for detailed status registers on PMBus
1.2 and newer devices. As with the existing older-device fallback,
CLEAR_FAULTS can clear other latched status; an active condition can
reassert its status.

Fixes: 35f165f08950 ("hwmon: (pmbus) Clear pmbus fault/warning bits after read")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Vishnu Razdan <vrazdan@openai.com>
Link: https://patch.msgid.link/20260824-vrazdan-pmbus-status-word-b4-v1-1-2606ecd0c029@openai.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hwmon/pmbus/pmbus_core.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -1166,7 +1166,9 @@ static int pmbus_get_boolean(struct i2c_
 
 	regval = status & mask;
 	if (regval) {
-		if (data->revision >= PMBUS_REV_12) {
+		/* Generic STATUS_WORD alarms are not individually clearable. */
+		if (data->revision >= PMBUS_REV_12 &&
+		    reg != PMBUS_STATUS_WORD) {
 			ret = _pmbus_write_byte_data(client, page, reg, regval);
 			if (ret)
 				goto unlock;