To summary
#1 Symptom:
On AMD EPYC, ROME server platform, SATA hot plug not working on Ubuntu 22.04
LTS.
#2 Root cause:
Ubuntu kernel compile with configure CONFIG_SATA_MOBILE_LPM_POLICY=3. During
devices scan ( boot, pci scan, ahci driver load), if didn't detected any valid
sata port or disk, it will power off the sata controller, so no event can get
when plug in sata disk.
It seems an expecting logic as AHCI spec shows that once LPM is enabled,
then the hotplug needs to be disabled.
# To enable hotplug by one of below 2 methods
a. Add below kernel parameter can make sata hot plug working
ahci.mobile_lpm_policy=1
In our test, set to 0 or 2 also works. Refer to #46 for what 0,1,2,3
represents.
b. via proc file
To set "max_performance" for
"/sys/class/scsi_host/host*/link_power_management_policy"
Set min_power or medium_power will enable power save and disable the "Hot
Plug" again.
# More info about mobile ALPM
Aggressive Link Power Management (ALPM) is a mechanism where a SATA AHCI
controller can put the SATA link that connects to the disk into a very low
power mode during periods of zero I/O activity and into an active power state
when work needs to be done. More refer to
https://wiki.ubuntu.com/Kernel/PowerManagementALPM.
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https://bugs.launchpad.net/bugs/1971576
Title:
SATA device hot plug regression on AMD EPYC (Asus) server
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