Patch "PCI: dwc: Fix enumeration end when reaching root subordinate" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

PCI: dwc: Fix enumeration end when reaching root subordinate

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pci-dwc-fix-enumeration-end-when-reaching-root-subordinate.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Koen Vandeputte <[email protected]>
Date: Wed, 7 Mar 2018 10:46:39 -0600
Subject: PCI: dwc: Fix enumeration end when reaching root subordinate

From: Koen Vandeputte <[email protected]>

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]

parent")

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

@@ -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 */

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/pci-dwc-fix-enumeration-end-when-reaching-root-subordinate.patch