Re: [PATCH 07/15] PCI/ASPM: Save L1SS state in the saved capability store

[Josh Hilke]

On Thu, Sep 24, 2026 at 10:34 AM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> Reserve PCI_L1SS_CTL1 and PCI_L1SS_CTL2 with a single request, since
> they are adjacent DWORDs, just as the old code allocated one two-DWORD
> buffer for both. Skip the reservation entirely for devices without the
> capability, which the previous code could not do because it allocated
> the buffer through pci_add_ext_cap_save_buffer() before looking at
> pdev->l1ss.

The last sentence needs rephrasing. The previous code didn't allocate a
buffer for devices without L1SS either: _pci_add_cap_save_buffer() did
its own pci_find_ext_capability() and returned 0 when the capability was
absent. The explicit "if (!pdev->l1ss) return;" in this patch is
required because pci_reserve_saved_cap() takes an offset, and
l1ss + PCI_L1SS_CTL1 with l1ss == 0 would hit the WARN_ON for offsets
below PCI_STD_HEADER_SIZEOF.


- Josh Hilke