On Fri, Jul 31, 2026 at 02:15:48PM -0700, Zhiping Zhang wrote: > get_rp_completer_type() returns the Root Port's "TPH Completer > Supported" field (bits 13:12 of Device Capabilities 2) verbatim. The > 0b10 encoding is reserved, but pcie_enable_tph() feeds the raw value > into the requester type: > > pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type); > > and later writes tph_req_type to the TPH Requester Enable field, which > only defines 0b00 (disable), 0b01 (TPH only) and 0b11 (extended TPH). > > No known hardware presents the reserved 0b10 in this field, so this is > defensive hardening rather than a fix for observed silicon: fold the > reserved encoding into "not supported" so only the three architected > values can ever reach the Requester Enable field. > > Signed-off-by: Zhiping Zhang <[email protected]> > Acked-by: Chengwen Feng <[email protected]>
In subject, to match history of the file: PCI/TPH: Treat reserved 0b10 completer encoding as unsupported Acked-by: Bjorn Helgaas <[email protected]> > --- > drivers/pci/tph.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c > index 655ffd60e62f..5cbb381e2a02 100644 > --- a/drivers/pci/tph.c > +++ b/drivers/pci/tph.c > @@ -200,6 +200,7 @@ EXPORT_SYMBOL(pcie_tph_get_st_table_size); > static u8 get_rp_completer_type(struct pci_dev *pdev) > { > struct pci_dev *rp; > + u8 tph_comp; > u32 reg; > int ret; > > @@ -211,7 +212,15 @@ static u8 get_rp_completer_type(struct pci_dev *pdev) > if (ret) > return 0; > > - return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg); > + /* > + * 0b10 is reserved; treat it as "not supported" so only the > + * architected encodings reach the Requester Enable field. > + */ > + tph_comp = FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg); > + if (tph_comp == PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY || > + tph_comp == PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH) > + return tph_comp; > + return PCI_EXP_DEVCAP2_TPH_COMP_NONE; > } > > /* Write tag to ST table - Return 0 if OK, otherwise -errno */ > -- > 2.53.0-Meta >
