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Flit mode introduced in PCIe r6.0 alters how the TLP Header Log is presented through AER and DPC Capability registers. The TLP Prefix Log Register is not present with Flit mode, and the register becomes an extension of the TLP Header Log (PCIe r6.1 secs 7.8.4.12 & 7.9.14.13). Adapt pcie_read_tlp_log() and struct pcie_tlp_log to read and store the extended TLP Header Log when the Link is in Flit mode. As the Prefix Log and Extended TLP Header are not present at the same time, a C union can be used. Determining whether the error occurred while the Link was in Flit mode is a bit complicated. In case of AER, the Advanced Error Capabilities and Control Register directly tells whether the error was logged in Flit mode or not (PCIe r6.1 sec 7.8.4.7). The DPC Capability (PCIe r6.1 sec 7.9.14), unfortunately, does not contain the same information. Unlike AER, the DPC Capability does not provide a way to discern whether the error was logged in Flit mode (this is confirmed by PCI WG to be an oversight in the spec). DPC will bring the Link down immediately following an error, which makes it impossible to acquire the Flit Mode Status directly from the Link Status 2 register because Flit Mode Status is only set in certain Link states (PCIe r6.1 sec 7.5.3.20). As a workaround, use the flit_mode value stored into the struct pci_bus. Link: https://lore.kernel.org/r/20250207161836.2755-3-ilpo.jarvinen@linux.intel.com Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>