[PATCH 4.15 043/146] PCI: dwc: Fix enumeration end when reaching root subordinate

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Koen Vandeputte <koen.vandeputte@xxxxxxxxxxxx>

commit fc110ebdd014dd1368c98e7685b47789c31fab42 upstream.

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 <niklas.cassel@xxxxxxxx>
Tested-by: Fabio Estevam <fabio.estevam@xxxxxxx>
Tested-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
Signed-off-by: Koen Vandeputte <koen.vandeputte@xxxxxxxxxxxx>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Acked-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx	# v4.15+
Cc: Binghui Wang <wangbinghui@xxxxxxxxxxxxx>
Cc: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Cc: Jianguo Sun <sunjianguo1@xxxxxxxxxx>
Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Cc: Minghuan Lian <minghuan.Lian@xxxxxxxxxxxxx>
Cc: Mingkai Hu <mingkai.hu@xxxxxxxxxxxxx>
Cc: Murali Karicheri <m-karicheri2@xxxxxx>
Cc: Pratyush Anand <pratyush.anand@xxxxxxxxx>
Cc: Richard Zhu <hongxing.zhu@xxxxxxx>
Cc: Roy Zang <tie-fei.zang@xxxxxxxxxxxxx>
Cc: Shawn Guo <shawn.guo@xxxxxxxxxx>
Cc: Stanimir Varbanov <svarbanov@xxxxxxxxxx>
Cc: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Cc: Xiaowei Song <songxiaowei@xxxxxxxxxxxxx>
Cc: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/pci/dwc/pcie-designware-host.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/pci/dwc/pcie-designware-host.c
+++ b/drivers/pci/dwc/pcie-designware-host.c
@@ -607,7 +607,7 @@ void dw_pcie_setup_rc(struct pcie_port *
 	/* 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 */