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Mon, 8 Mar 2021 22:54:30 +0000 (GMT) Received: from v0005c16.aus.stglabs.ibm.com (unknown [9.211.41.147]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 8 Mar 2021 22:54:30 +0000 (GMT) From: Eddie James To: openbmc@lists.ozlabs.org Subject: [PATCH linux dev-5.10 35/35] pmbus: (max31785) Retry enabling fans after writing MFR_FAN_CONFIG Date: Mon, 8 Mar 2021 16:54:19 -0600 Message-Id: <20210308225419.46530-36-eajames@linux.ibm.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20210308225419.46530-1-eajames@linux.ibm.com> References: <20210308225419.46530-1-eajames@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-03-08_20:2021-03-08, 2021-03-08 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 impostorscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103080118 X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" From: Andrew Jeffery It has been observed across large fleets of systems that a small subset of those systems occasionally loose control of some number of fans across a BMC reboot (their hwmon fan attributes are missing from sysfs). >>From extensive testing and tracing it was discovered that writes enabling a fan in FAN_CONFIG_1_2 failed to stick on the system under test with a frequency of about 1 in 1000 re-binds of the driver. The MAX31785 datasheet recommends in the documentation for MFR_FAN_CONFIG that the asssociated fan(s) be disabled before updating the register. The sequence in question implements this suggestion, and the observed loss-of-fans symptom occurs when the write to re-enable the fan in FAN_CONFIG_1_2 fails to stick. The trace data suggests a one-shot retry is enough to successfully update FAN_CONFIG_1_2. With the workaround, no loss of fans was observed in over 20,000 consecutive rebinds of the driver. OpenBMC-Staging-Count: 1 Signed-off-by: Andrew Jeffery Signed-off-by: Joel Stanley --- drivers/hwmon/pmbus/max31785.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c index 1e021c38d507..0c2fe22018a3 100644 --- a/drivers/hwmon/pmbus/max31785.c +++ b/drivers/hwmon/pmbus/max31785.c @@ -398,6 +398,7 @@ static int max31785_of_fan_config(struct i2c_client *client, u32 page; u32 uval; int ret; + int i; if (!of_device_is_compatible(child, "pmbus-fan")) return 0; @@ -574,10 +575,24 @@ static int max31785_of_fan_config(struct i2c_client *client, if (ret < 0) return ret; - ret = max31785_i2c_smbus_write_byte_data(client, PMBUS_FAN_CONFIG_12, - pb_cfg); - if (ret < 0) - return ret; + for (i = 0; i < 2; i++) { + ret = max31785_i2c_smbus_write_byte_data(client, + PMBUS_FAN_CONFIG_12, + pb_cfg); + if (ret < 0) + continue; + + ret = max31785_i2c_smbus_read_byte_data(client, + PMBUS_FAN_CONFIG_12); + if (ret < 0) + continue; + + if (ret == pb_cfg) + break; + } + + if (i == 2) + return -EIO; /* * Fans are on pages 0 - 5. If the page property of a fan node is -- 2.27.0