Re: [PATCH v2 2/2] PCI: pciehp: Prevent deadlock on disconnect

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Wed, Oct 23, 2019 at 10:52:53AM +0300, Mika Westerberg wrote:
> > Shouldn't we check for slot_status being an error response (~0)
> > instead of looking for PCIBIOS_DEVICE_NOT_FOUND?  There are 7 RsvdP
> > bits in Slot Status, so ~0 is not a valid value for the register.
> > 
> > All 16 bits of Link Status are defined, but ~0 is still an invalid
> > value because the Current Link Speed and Negotiated Link Width fields
> > only define a few valid encodings.
> 
> Indeed that's a good point. I'll try that.

Just checking if I understand correctly what you are suggesting.

Currently we use pcie_capability_read_word() and check the return value.
If the device is gone it returns an error and resets *val to 0. That
only works if pci_dev_is_disconnected() is true so we would need to do
something like below.

pciehp_check_link_active():

	ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
	if (ret == PCIBIOS_DEVICE_NOT_FOUND || lnk_status == (u16)~0)
		return -ENODEV;

Or you mean that we check only for ~0 in which case we either need to
use pci_read_config_word() directly here or modify pcie_capability_read_word()
return ~0 instead of clearing it?