When the link does not come up within the training timeout, the probe returns -ENODEV. An empty slot is a normal configuration, but the failed probe leaves the root port unusable, skips the outbound memory window, and makes every later lookup of the bus (each "pci" command, a boot device scan) probe the controller again, repeating the whole bring-up and the one second wait.
Linux's DesignWare core carries on when the link does not come up and only refuses config requests to the buses behind the root port while the link is down (dw_pcie_other_conf_map_bus()); FreeBSD's spacemit_pcie driver also treats a down link as non-fatal. Do the same: report the link as down, finish the probe, and answer config reads behind the root port with all ones, dropping writes, while the link is down. Signed-off-by: Dave Klotz <[email protected]> --- drivers/pci/pcie_dw_spacemit.c | 53 +++++++++++++++++++++++++++------- 1 file changed, 43 insertions(+), 10 deletions(-) diff --git a/drivers/pci/pcie_dw_spacemit.c b/drivers/pci/pcie_dw_spacemit.c index 9b299ca17a..61c759172d 100644 --- a/drivers/pci/pcie_dw_spacemit.c +++ b/drivers/pci/pcie_dw_spacemit.c @@ -338,15 +338,18 @@ static int pcie_dw_spacemit_probe(struct udevice *dev) pcie_dw_setup_host(&pci->dw); pcie_dw_init_id(pci); - if (!pcie_dw_spacemit_pcie_link_up(pci)) { + /* + * An empty slot, or a device that does not train, is not an error: + * the root port is still usable and the config accessors keep + * requests for the buses behind it off the wire. + */ + if (!pcie_dw_spacemit_pcie_link_up(pci)) printf("PCIE-%d: Link down\n", dev_seq(dev)); - return -ENODEV; - } - - printf("PCIE-%d: Link up (Gen%d-x%d, Bus%d)\n", dev_seq(dev), - pcie_dw_get_link_speed(&pci->dw), - pcie_dw_get_link_width(&pci->dw), - hose->first_busno); + else + printf("PCIE-%d: Link up (Gen%d-x%d, Bus%d)\n", dev_seq(dev), + pcie_dw_get_link_speed(&pci->dw), + pcie_dw_get_link_width(&pci->dw), + hose->first_busno); ret = pcie_dw_prog_outbound_atu_unroll(&pci->dw, PCIE_ATU_REGION_INDEX0, PCIE_ATU_TYPE_MEM, @@ -430,9 +433,39 @@ static int pcie_dw_spacemit_of_to_plat(struct udevice *dev) return 0; } +/* + * Nothing answers behind the root port while the link is down, so do not + * send config requests there; Linux's DesignWare core does the same. + */ +static int pcie_dw_spacemit_read_config(const struct udevice *bus, + pci_dev_t bdf, uint offset, + ulong *valuep, enum pci_size_t size) +{ + struct pcie_dw_spacemit *pci = dev_get_priv(bus); + + if (PCI_BUS(bdf) != pci->dw.first_busno && !is_link_up(pci)) { + *valuep = pci_get_ff(size); + return 0; + } + + return pcie_dw_read_config(bus, bdf, offset, valuep, size); +} + +static int pcie_dw_spacemit_write_config(struct udevice *bus, pci_dev_t bdf, + uint offset, ulong value, + enum pci_size_t size) +{ + struct pcie_dw_spacemit *pci = dev_get_priv(bus); + + if (PCI_BUS(bdf) != pci->dw.first_busno && !is_link_up(pci)) + return 0; + + return pcie_dw_write_config(bus, bdf, offset, value, size); +} + static const struct dm_pci_ops pcie_dw_spacemit_ops = { - .read_config = pcie_dw_read_config, - .write_config = pcie_dw_write_config, + .read_config = pcie_dw_spacemit_read_config, + .write_config = pcie_dw_spacemit_write_config, }; static const struct udevice_id pcie_dw_spacemit_ids[] = { -- 2.55.0
