> max_link_speed, max_link_width, current_link_speed and current_link_width
> have been exported under /sys/bus/pci/devices/.../ since 2018, by
> commit 56c1af4606f0 ("PCI: Add sysfs max_link_speed/width, current_link_speed/width, etc"),
> and none of the four appear anywhere in Documentation/ABI.
>
> The gap matters most for current_link_speed. current_link_speed_show()
> performs a fresh PCI_EXP_LNKSTA read on every open, so the value reflects
> the link state at that instant. Modern GPUs retrain their link continuously
> as part of idle power management, which means a single read can legitimately
> return any speed the link supports, not the speed the link will use under
> load.
>
> Observed on an RTX 5070 in a PCIe 4.0 x16 slot, same boot, no configuration
> change between the two reads: 5.0 GT/s while idle, 16.0 GT/s under load.
> Comparing current_link_speed against max_link_speed at idle is therefore not
> [ ... ]
> end's capability rather than the link's.
>
> No functional change.
>
> Signed-off-by: Ferran Duarri <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1
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