[openwrt/openwrt] kernel: backport pcie enumeration fix to kernel 4.9

[LEDE Commits]

blogic pushed a commit to openwrt/openwrt.git, branch master:
https://git.lede-project.org/2f85985da245c1220695746384b9020dd6dc7848

commit 2f85985da245c1220695746384b9020dd6dc7848
Author: Koen Vandeputte <koen.vandeputte at ncentric.com>
AuthorDate: Mon Feb 19 10:46:14 2018 +0100

    kernel: backport pcie enumeration fix to kernel 4.9
    
    This issue is also present in kernel 4.9 starting from 4.9.71
    Adapted the patch, as the fixed function is in another location here.
    
    Signed-off-by: Koen Vandeputte <koen.vandeputte at ncentric.com>
---
 .../pending-4.9/812-pci-dwc-fix-enumeration.patch  | 62 ++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/target/linux/generic/pending-4.9/812-pci-dwc-fix-enumeration.patch b/target/linux/generic/pending-4.9/812-pci-dwc-fix-enumeration.patch
new file mode 100644
index 0000000..5092aba
--- /dev/null
+++ b/target/linux/generic/pending-4.9/812-pci-dwc-fix-enumeration.patch
@@ -0,0 +1,62 @@
+From patchwork Tue Jan  9 14:42:21 2018
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: PCI: dwc: fix enumeration end when reaching root subordinate
+From: Koen Vandeputte <koen.vandeputte at ncentric.com>
+X-Patchwork-Id: 10152443
+Message-Id: <1515508941-20055-1-git-send-email-koen.vandeputte at ncentric.com>
+To: linux-pci at vger.kernel.org
+Cc: bhelgaas at google.com, lorenzo.pieralisi at arm.com,
+ Joao.Pinto at synopsys.com, jingoohan1 at gmail.com, niklas.cassel at axis.com,
+ Koen Vandeputte <koen.vandeputte at ncentric.com>,
+ Mika Westerberg <mika.westerberg at linux.intel.com>
+Date: Tue,  9 Jan 2018 15:42:21 +0100
+
+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, meaning
+that all busses [0x00-0xff] are reachable through this RC.
+
+Fixes: a20c7f36bd3d ("PCI: Do not allocate more buses than available in
+parent")
+Signed-off-by: Koen Vandeputte <koen.vandeputte at ncentric.com>
+Tested-by: Niklas Cassel <niklas.cassel at axis.com>
+Cc: Mika Westerberg <mika.westerberg at linux.intel.com>
+---
+
+Will send separate patches to stable as this file got moved/renamed
+
+
+ drivers/pci/host/pcie-designware.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c
+index bf558df5b7b3..2b5470173196 100644
+--- a/drivers/pci/host/pcie-designware.c
++++ b/drivers/pci/host/pcie-designware.c
+@@ -861,7 +861,7 @@ void dw_pcie_setup_rc(struct pcie_port *
+ 	/* setup bus numbers */
+ 	val = dw_pcie_readl_rc(pp, PCI_PRIMARY_BUS);
+ 	val &= 0xff000000;
+-	val |= 0x00010100;
++	val |= 0x00ff0100;
+ 	dw_pcie_writel_rc(pp, PCI_PRIMARY_BUS, val);
+ 
+ 	/* setup command register */