mvebu: reduce speed to gen1 for espressobin pcie

Since the beginning there's been an issue with initializing the Atheros
based MiniPCIe wireless cards. Here's an example of kerenel log:

 OF: PCI: host bridge /soc/pcie@d0070000 ranges:
 OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
 OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
 advk-pcie d0070000.pcie: link up
 advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
 pci_bus 0000:00: root bus resource [bus 00-ff]
 pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
 pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address[0xe9000000-0xe900ffff])
 pci 0000:00:00.0: BAR 0: assigned [mem0xe8000000-0xe801ffff 64bit]
 pci 0000:00:00.0: BAR 6: assigned [mem0xe8020000-0xe802ffff pref]
 [...]
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x44
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 ath9k 0000:00:00.0: enabling device (0000 -> 0002)
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0xc
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x40
 ath9k 0000:00:00.0: request_irq failed
 advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
 ath9k: probe of 0000:00:00.0 failed with error -22

The same happens for ath5k cards, while ath10k card didn't appear at
all (not detected):

 OF: PCI: host bridge /soc/pcie@d0070000 ranges:
 OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
 OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
 advk-pcie d0070000.pcie: link never came up
 advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
 pci_bus 0000:00: root bus resource [bus 00-ff]
 pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
 pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address[0xe9000000-0xe900ffff])
 advk-pcie d0070000.pcie: config read/write timed out

Following the issue on esppressobin.net forum [1] the workaround seems
to be limiting the speed of PCIe bridge to 1st generation. This fixed
the initialisation of all tested Atheros wireless cards.

The change shouldn't affect the performance for wireless cards,
it could reduce the performance of storage controller cards but since
OpenWrt focuses on wireless connectivity, fixing compatibility with
wireless cards should be a priority.

For the record, the iwlwifi and mt76 cards were not affected by this
issue.

1. http://espressobin.net/forums/topic/which-pcie-wlan-cards-are-supported

Signed-off-by: Tomasz Maciej Nowak <tomek_n@o2.pl>

1 files changed, 73 insertions, 0 deletions

diff --git a/target/linux/mvebu/patches-4.14/528-arm64-dts-armada-3720-espressobin-set-max-link-to-ge.patch b/target/linux/mvebu/patches-4.14/528-arm64-dts-armada-3720-espressobin-set-max-link-to-ge.patch
new file mode 100644
index 0000000000..5ff9b47268
--- /dev/null
+++ b/target/linux/mvebu/patches-4.14/528-arm64-dts-armada-3720-espressobin-set-max-link-to-ge.patch
@@ -0,0 +1,73 @@
+From 33f8fdcedb01680427328d710594facef7a0092c Mon Sep 17 00:00:00 2001
+From: Tomasz Maciej Nowak <tmn505@gmail.com>
+Date: Thu, 14 Jun 2018 14:40:26 +0200
+Subject: [PATCH 2/2] arm64: dts: armada-3720-espressobin: set max link to gen1
+
+Since the beginning there's been an issue with initializing the Atheros
+based MiniPCIe wireless cards. Here's an example of kerenel log:
+
+ OF: PCI: host bridge /soc/pcie@d0070000 ranges:
+ OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
+ OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
+ advk-pcie d0070000.pcie: link up
+ advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
+ pci_bus 0000:00: root bus resource [bus 00-ff]
+ pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
+ pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address [0xe9000000-0xe900ffff])
+ pci 0000:00:00.0: BAR 0: assigned [mem0xe8000000-0xe801ffff 64bit]
+ pci 0000:00:00.0: BAR 6: assigned [mem0xe8020000-0xe802ffff pref]
+ [...]
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x44
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
+ ath9k 0000:00:00.0: enabling device (0000 -> 0002)
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x3c
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0xc
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x40
+ ath9k 0000:00:00.0: request_irq failed
+ advk-pcie d0070000.pcie: Posted PIO Response Status: CA,0xe00 @ 0x4
+ ath9k: probe of 0000:00:00.0 failed with error -22
+
+The same happens for ath5k cards, while ath10k card didn't appear at
+all (not detected):
+
+ OF: PCI: host bridge /soc/pcie@d0070000 ranges:
+ OF: PCI:   MEM 0xe8000000..0xe8ffffff -> 0xe8000000
+ OF: PCI:    IO 0xe9000000..0xe900ffff -> 0xe9000000
+ advk-pcie d0070000.pcie: link never came up
+ advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00
+ pci_bus 0000:00: root bus resource [bus 00-ff]
+ pci_bus 0000:00: root bus resource [mem0xe8000000-0xe8ffffff]
+ pci_bus 0000:00: root bus resource [io  0x0000-0xffff](bus address [0xe9000000-0xe900ffff])
+ advk-pcie d0070000.pcie: config read/write timed out
+
+Following the issue on esppressobin.net forum [1] the workaround seems
+to be limiting the speed of PCIe bridge to 1st generation. This fixed
+the initialisation of all tested Atheros wireless cards.
+The patch in the forum thread swaped registers which would limit speed
+for all Armada 3700 based boards. The approach in this patch, in
+conjunction with "PCI: aardvark: allow to specify link capability" patch
+is less invasive, it only touches the affected board.
+
+For the record, the iwlwifi and mt76 cards were not affected by this
+issue.
+
+1. http://espressobin.net/forums/topic/which-pcie-wlan-cards-are-supported
+
+Signed-off-by: Tomasz Maciej Nowak <tmn505@gmail.com>
+---
+ arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
++++ b/arch/arm64/boot/dts/marvell/armada-3720-espressobin.dts
+@@ -79,6 +79,8 @@
+ /* J9 */
+ &pcie0 {
+ 	status = "okay";
++
++	max-link-speed = <1>;
+ };
+ 
+ /* J6 */