Re: [PATCH v3] PCI: Disable ASPM L0s for Realtek RTS525A

[Lukas Wunner <lukas@wunner.de>]

On Mon, Jul 06, 2026 at 10:53:58AM +0800, Max Lee wrote:
> The Realtek RTS525A PCIe card reader reports an AER Correctable Replay
> Timer Timeout storm when ASPM L0s is enabled on its link.  On an affected
> HP ZBook Power 16 inch G11, the Root Port received tens of millions of
> AER interrupts from the RTS525A even when the rtsx_pci driver was
> blacklisted and the endpoint was not enabled by a driver.
> 
> Testing with OS-native AER control showed that disabling only L0s on the
> RTS525A link stops new AER interrupt and counter growth while leaving L1
> enabled.  Disabling L1, L1 substates, or Clock PM alone did not stop the
> storm.
> 
> Prevent the broken L0s configuration by removing L0s from the RTS525A
> advertised ASPM capability.  This avoids enabling the non-working ASPM
> state instead of masking the resulting AER Replay Timer Timeout reports.
> 
> Signed-off-by: Max Lee <max.lee@canonical.com>

Reviewed-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org

Thanks for your great analysis in:

https://lore.kernel.org/r/CA+YcyLw0HpR1Dnz-mOL1Ryym89ytc=1a_Ri9buMt3at-9mib+g@mail.gmail.com/

In fact a quick Google search finds other reports of ASPM issues with
this card reader.  This one is for Linux and talks about Receiver Errors
with RTS525A which are fixed by pcie_aspm=off, a more targeted fix was
apparently not developed:

https://github.com/pop-os/pop/issues/3775

And another one for macOS specifically mentioning non-working L0s on
RTS525A:

https://github.com/5T33Z0/OC-Little-Translated/blob/main/Content/04_Fixing_Sleep_and_Wake_Issues/Setting_ASPM_Operating_Mode/README.md

It looks like this product just doesn't support L0s and the vendor
neglected to set the ASPM Support bits in the Link Capabilities Register
correctly.

Thanks,

Lukas