PCI: dwc: Fix enumeration end when reaching root subordinate

The subordinate value indicates the highest bus number which can be
reached downstream though a certain device.

Commit a20c7f36bd3d ("PCI: Do not allocate more buses than available in
parent") ensures that downstream devices cannot assign busnumbers higher
than the upstream device subordinate number, which was indeed illogical.

By default, dw_pcie_setup_rc() inits the Root Complex subordinate to a
value of 0x01.

Due to this combined with above commit, enumeration stops digging deeper
downstream as soon as bus num 0x01 has been assigned, which is always the
case for a bridge device.

This results in all devices behind a bridge bus remaining undetected, as
these would be connected to bus 0x02 or higher.

Fix this by initializing the RC to a subordinate value of 0xff, which is
not altering hardware behaviour in any way, but informs probing function
pci_scan_bridge() later on which reads this value back from register.

The following nasty errors during boot are also fixed by this:

  pci_bus 0000:02: busn_res: can not insert [bus 02-ff] under [bus 01] (conflicts with (null) [bus 01])
  ...
  pci_bus 0000:03: [bus 03] partially hidden behind bridge 0000:01 [bus 01]
  ...
  pci_bus 0000:04: [bus 04] partially hidden behind bridge 0000:01 [bus 01]
  ...
  pci_bus 0000:05: [bus 05] partially hidden behind bridge 0000:01 [bus 01]
  pci_bus 0000:02: busn_res: [bus 02-ff] end is updated to 05
  pci_bus 0000:02: busn_res: can not insert [bus 02-05] under [bus 01] (conflicts with (null) [bus 01])
  pci_bus 0000:02: [bus 02-05] partially hidden behind bridge 0000:01 [bus 01]

Fixes: a20c7f36bd3d ("PCI: Do not allocate more buses than available in
parent")
Tested-by: Niklas Cassel <[email protected]>
Tested-by: Fabio Estevam <[email protected]>
Tested-by: Sebastian Reichel <[email protected]>
Signed-off-by: Koen Vandeputte <[email protected]>
Signed-off-by: Lorenzo Pieralisi <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Acked-by: Lucas Stach <[email protected]>
Cc: [email protected]	# v4.15+
Cc: Binghui Wang <[email protected]>
Cc: Jesper Nilsson <[email protected]>
Cc: Jianguo Sun <[email protected]>
Cc: Jingoo Han <[email protected]>
Cc: Kishon Vijay Abraham I <[email protected]>
Cc: Lucas Stach <[email protected]>
Cc: Mika Westerberg <[email protected]>
Cc: Minghuan Lian <[email protected]>
Cc: Mingkai Hu <[email protected]>
Cc: Murali Karicheri <[email protected]>
Cc: Pratyush Anand <[email protected]>
Cc: Richard Zhu <[email protected]>
Cc: Roy Zang <[email protected]>
Cc: Shawn Guo <[email protected]>
Cc: Stanimir Varbanov <[email protected]>
Cc: Thomas Petazzoni <[email protected]>
Cc: Xiaowei Song <[email protected]>
Cc: Zhou Wang <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
index 8de2d5c69b1d..dc9303abda42 100644
--- a/drivers/pci/dwc/pcie-designware-host.c
+++ b/drivers/pci/dwc/pcie-designware-host.c
@@ -613,7 +613,7 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 	/* setup bus numbers */
 	val = dw_pcie_readl_dbi(pci, PCI_PRIMARY_BUS);
 	val &= 0xff000000;
-	val |= 0x00010100;
+	val |= 0x00ff0100;
 	dw_pcie_writel_dbi(pci, PCI_PRIMARY_BUS, val);
 
 	/* setup command register */