FAILED: patch "[PATCH] PCI: dwc: Fix enumeration end when reaching root subordinate" failed to apply to 4.17-stable tree

The patch below does not apply to the 4.17-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Koen Vandeputte <[email protected]>
Date: Mon, 15 Jan 2018 10:36:08 +0100
Subject: [PATCH] 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 to remain 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.

Following nasty errors during boot are also fixed by this:

[    0.459145] pci_bus 0000:02: busn_res: can not insert [bus 02-ff]
under [bus 01] (conflicts with (null) [bus 01])
...
[    0.464515] pci_bus 0000:03: [bus 03] partially hidden behind bridge
0000:01 [bus 01]
...
[    0.464892] pci_bus 0000:04: [bus 04] partially hidden behind bridge
0000:01 [bus 01]
...
[    0.466488] pci_bus 0000:05: [bus 05] partially hidden behind bridge
0000:01 [bus 01]
[    0.466506] pci_bus 0000:02: busn_res: [bus 02-ff] end is updated to
05
[    0.466517] pci_bus 0000:02: busn_res: can not insert [bus 02-05]
under [bus 01] (conflicts with (null) [bus 01])
[    0.466534] pci_bus 0000:02: [bus 02-05] partially hidden behind

bridge 0000:01 [bus 01]

parent")

index 8de2d5c69b1d..dc9303abda42 100644
@@ -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 */