Re: [PATCH] pci: ensure valid link status bits for downstream ports

[Sebastian Ott]

On Mon, 11 Nov 2024, Sebastian Ott wrote:
> PCI hotplug for downstream endpoints on arm fails because Linux'
> PCIe hotplug driver doesn't like the QEMU provided LNKSTA:
>
>  pcieport 0000:08:01.0: pciehp: Slot(2): Card present
>  pcieport 0000:08:01.0: pciehp: Slot(2): Link Up
>  pcieport 0000:08:01.0: pciehp: Slot(2): Cannot train link: status 0x2000
>
> There's 2 cases where LNKSTA isn't setup properly:
> * the downstream device has no express capability

I stumbled over this while debugging - is a pci device attached
to a pcie downstream even a valid usecase?

> * max link width of the bridge is 0

MLW for the downstream is initialized with defaults but gets overwritten
later because speed and width properties are 0. Dunno if that's the issue
we should address?

Sebastian