[PATCH] PCI/ASPM: Enable only L0s and L1 for devicetree platforms

[Christian Zigotzky]

> On 29 October 2025 at 00:33 am, Bjorn Helgaas <helgaas at kernel.org> wrote:
> 
> On Mon, Oct 27, 2025 at 06:12:24PM +0100, Christian Zigotzky wrote:
>> Hi All,
>> 
>> I activated CONFIG_PCIEASPM and CONFIG_PCIEASPM_DEFAULT again for the RC3 of
>> kernel 6.18. Unfortunately my AMD Radeon HD6870 doesn't work with the latest
>> patches.
>> 
>> But that doesn't matter because we disable the above kernel options by
>> default. We don't need power management for PCI Express because of boot
>> issues and performance issues.
> 
> If you have a chance, could you try the patch below on top of
> v6.18-rc3 with CONFIG_PCIEASPM=y?
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 214ed060ca1b..2b6d4e0958aa 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -2524,6 +2524,7 @@ static void quirk_disable_aspm_l0s_l1(struct pci_dev *dev)
>  * disable both L0s and L1 for now to be safe.
>  */
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ASMEDIA, 0x1080, quirk_disable_aspm_l0s_l1);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_FREESCALE, 0x0451, quirk_disable_aspm_l0s_l1);
> 
> /*
>  * Some Pericom PCIe-to-PCI bridges in reverse mode need the PCIe Retrain

Thanks for the patch. 

I will test it on my FSL Cyrus+ board over the weekend.
BTW, I also tested my PASemi Nemo board with the RC3 of kernel 6.18 and with power management for PCI Express enabled. Unfortunately, the installed AMD Radeon HD5870 does not work with power management for PCI Express enabled either.

Power management for PCI Express is not interesting for our machines because it is somewhat slower and we do not want power management to impair performance.
But it is a good thing for 24/7 servers.

- Christian