Re: [REGRESSION] libata: SATA LPM forcibly disabled on Intel Jasper Lake since Linux 6.13

[Bernard Drozd]

Hi Damien,

thank you for the detailed explanation – that was exactly the missing piece.
You were absolutely right: the issue was caused by all SATA ports being 
reported by the BIOS as external (hot-pluggable).

In my BIOS (AMI Aptio), all SATA ports had Hot Plug enabled by default:
https://www.dropbox.com/scl/fi/9gi68rlxg1mcd37yrwcva/Hot_PLUG_SATA.jpg?rlkey=cse0i5j7qr4va0xjw9o7fv6r4&st=dn6r6q0k&raw=1
After disabling Hot Plug for the SATA ports, LPM works correctly again.

Results:
- Kernel: 6.17.8-1~bpo13+1
- link_power_management_policy can now be set to: med_power_with_dipm
- SATA links enter partial/slumber
- CPU package reaches deep C-states again (PC10)
- Idle power consumption back to ~2.5 W (same as with 6.12)

So this was not a kernel regression, but a correct behavior exposed by 
the libata fix after 6.12, combined with an unfortunate BIOS default.
Thanks again for the clear analysis and for pointing out 
ahci.mask_port_ext as a fallback – very helpful.

Best regards,
Bernard

On 15/12/2025 07:47, Damien Le Moal wrote:
> On 12/15/25 13:28, Bernard Drozd wrote:
> > Hi Damien,
> > Thank you for the explanation – I understand now that pre-6.13 behaviour
> > was relying on a bug allowing userspace to override unsupported LPM.
> > I have collected full diagnostics comparing a *working* kernel (6.12)
> > and a *regressed* kernel (6.17), both tested with **no SATA devices
> > connected**.
> >
> > Important correction:
> > The correct SATA controller PCI ID is:
> > Intel Jasper Lake SATA AHCI Controller [8086:4dd3]
> > This was mistakenly reported earlier as 4d03.
> >
> > Key observation:
> > The LPM disable happens even with no SATA devices attached, so this
> > appears to be a **platform-level decision**, not device capability.
> >
> > Data provided:
> > 1) Full dmesg, Linux 6.12 (LPM works, CPU reaches PC10):
> > https://www.dropbox.com/scl/fi/pwc0bfgoqgb607babczg9/dmesg-6.12-full.txt?rlkey=o8j88lzeq3rw3cbx2q65oyblv&st=u4dwqv0p&raw=1
> >
> > 2) Full dmesg, Linux 6.17 (LPM forced to max_performance, CPU stuck in PC2):
> > https://www.dropbox.com/scl/fi/twbyjm7h5ewgmllit02h8/dmesg-6.17-full.txt?rlkey=p3b97lli6ruo5ypg4c2d4jnc2&st=3o3xo47m&raw=1
> Got it: your AHCI adapter has:
>
> ahci 0000:00:17.0: AHCI vers 0001.0301, 32 command slots, 6 Gbps, SATA mode
> ahci 0000:00:17.0: 2/2 ports implemented (port mask 0x3)
> ahci 0000:00:17.0: flags: 64bit ncq sntf pm led clo only pio slum part deso sadm sds
>
> Partial and slumber are supported, so all good.
>
> BUT ! your ports are...
>
> ata1: SATA max UDMA/133 abar m2048@0x80102000 port 0x80102100 irq 142 lpm-pol 1 ext
> ata2: SATA max UDMA/133 abar m2048@0x80102000 port 0x80102180 irq 142 lpm-pol 1 ext
>
> ...external. That is, the adapter is saying that these are
> external/hot-pluggable ports, and for these, power management is a bad
> idea/should be disabled, which we do. The reason is that otherwise, we cannot
> catch hot-plug/unplug events (IRQs).
>
> So to enable low-power policies, you need to go into your BIOS settings and
> disable the hot-plugging capability for the ports. Many BIOSes have such setting
> for SATA ports. If your BIOS does not have this, yu can use the mask_port_ext
> AHCI module parameter. Simply add:
>
> ahci.mask_port_ext=0x3 to your kernel command line and the "ext" flag of the
> ports will be ignored and LPM enabled.