pcie-brcmstb: failed to enter low-power link state (L23)

[Florian Fainelli]

Hi Stefan,

On 12/27/24 04:44, Stefan Wahren wrote:
> Hi,
> I did some experiments with s2idle on Raspberry Pi 4 (8 GB RAM,
> arm64/defconfig) and noticed that pcie-brcmstb fails to enter L23 state
> during suspend. I don't have any clue about PCI or this specific IP.
> 
> Here is my current working branch [1], because s2idle on BCM2711
> currently requires some quirks.
> 
> In order to help, I just added a simple dump of possible relevant
> registers at the begin of brcm_pcie_enter_l23():
> 
> [   46.822440] PM: suspend entry (s2idle)
> [   47.050887] Filesystems sync: 0.228 seconds
> [   47.152159] Freezing user space processes
> [   47.154443] Freezing user space processes completed (elapsed 0.002
> seconds)
> [   47.154472] OOM killer disabled.
> [   47.154475] Freezing remaining freezable tasks
> [   47.155742] Freezing remaining freezable tasks completed (elapsed
> 0.001 seconds)
> [   48.797565] PM: suspend of devices complete after 1641.374 msecs
> [   48.797580] PM: start suspend of devices complete after 1641.829 msecs
> [   48.798059] PM: late suspend of devices complete after 0.473 msecs
> [   48.810510] brcm-pcie fd500000.pcie:
> PCIE_RC_CFG_PRIV1_LINK_CAPABILITY: 00315e12
> [   48.810519] brcm-pcie fd500000.pcie: PCIE_RC_CFG_PRIV1_ROOT_CAP: 
> 0000000f
> [   48.810523] brcm-pcie fd500000.pcie: PCIE_MISC_HARD_PCIE_HARD_DEBUG:
> 00200000
> [   48.810528] brcm-pcie fd500000.pcie: PCIE_MISC_MISC_CTRL: 88003480
> [   48.810532] brcm-pcie fd500000.pcie: PCIE_MISC_PCIE_CTRL: 00000000
> [   48.810535] brcm-pcie fd500000.pcie: PCIE_MISC_PCIE_STATUS: 000000b0
> [   48.846632] brcm-pcie fd500000.pcie: failed to enter low-power link 
> state
> [   48.846640] xhci_hcd 0000:01:00.0: Possible wake-up device;
> regulators will not be disabled
> [   48.846725] PM: noirq suspend of devices complete after 48.628 msecs
> [   48.846730] PM: suspend-to-idle
> [   53.672017] PM: Triggering wakeup from IRQ 25
> [   53.672032] PM: resume from suspend-to-idle
> 
> Does BCM2711 support L23 mode?

AFAICT it does, but the end-point might not, and this is not considered 
a fatal error, in fact we should probably demote this message. Would you 
have the lspci -vvv of the XHCI controller, too?
-- 
Florian