nopnopnop:

The device is TP-Link Archer C50.
The LEDE version is: LEDE Reboot SNAPSHOT r4650-5d7e23f

How to reproduce:
1 compile LEDE for rampis, Archer C50
2 boot the device
3 5 GHz radio doesn't work

[ 0.000000] Linux version 4.9.40 (wrt@3ea47871fe5c) (gcc version 5.4.0 (LEDE GCC 5.4.0 r4650-5d7e23f) ) #0 Sat Jul 29 07:24:32 2017
[ 0.000000] Board has DDR2
[ 0.000000] Analog PMU set to hw control
[ 0.000000] Digital PMU set to hw control
[ 0.000000] SoC Type: MediaTek MT7620A ver:2 eco:6
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019650 (MIPS 24KEc)
[ 0.000000] MIPS: machine is TP-Link Archer C50
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 04000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
[ 0.000000] Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] On node 0 totalpages: 16384
[ 0.000000] free_area_init_node: node 0, pgdat 803f6ef4, node_mem_map 81000020
[ 0.000000] Normal zone: 128 pages used for memmap
[ 0.000000] Normal zone: 0 pages reserved
[ 0.000000] Normal zone: 16384 pages, LIFO batch:3
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=132768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256
[ 0.000000] Kernel command line: console=ttyS0,115200 rootfstype=squashfs,jffs2
[ 0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
[ 0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Writing ErrCtl register=0007fb00
[ 0.000000] Readback ErrCtl register=0007fb00
[ 0.000000] Memory: 60424K/65536K available (3152K kernel code, 156K rwdata, 756K rodata, 152K init, 216K bss, 5112K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:256
[ 0.000000] CPU Clock: 580MHz
[ 0.000000] clocksource: systick: mask: 0xffff max_cycles: 0xffff, max_idle_ns: 583261500 ns
[ 0.000000] systick: enable autosleep mode
[ 0.000000] systick: running - mult: 214748, shift: 32
[ 0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 6590553264 ns
[ 0.000012] sched_clock: 32 bits at 290MHz, resolution 3ns, wraps every 7405115902ns
[ 0.007578] Calibrating delay loop... 385.84 BogoMIPS (lpj=1929216)
[ 0.070070] pid_max: default: 32768 minimum: 301
[ 0.074687] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.081063] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.094852] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[ 0.104396] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.110358] pinctrl core: initialized pinctrl subsystem
[ 0.116064] NET: Registered protocol family 16
[ 0.454267] mt7620-pci 10140000.pcie: MT7620 PPLL unlock
[ 0.459410] mt7620-pci: probe of 10140000.pcie failed with error -1
[ 0.478719] rt2880_gpio 10000600.gpio: registering 24 gpios
[ 0.484170] rt2880_gpio 10000600.gpio: registering 24 irq handlers
[ 0.490501] rt2880_gpio 10000638.gpio: registering 16 gpios
[ 0.495922] rt2880_gpio 10000638.gpio: registering 16 irq handlers
[ 0.502158] rt2880_gpio 10000660.gpio: registering 32 gpios
[ 0.507566] rt2880_gpio 10000660.gpio: registering 32 irq handlers
[ 0.513805] rt2880_gpio 10000688.gpio: registering 1 gpios
[ 0.519130] rt2880_gpio 10000688.gpio: registering 1 irq handlers
[ 0.529008] clocksource: Switched to clocksource systick
[ 0.535464] NET: Registered protocol family 2
[ 0.540614] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.547339] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.553563] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.559787] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.565411] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.571774] NET: Registered protocol family 1
[ 0.575966] PCI: CLS 0 bytes, default 32
[ 0.578225] rt-timer 10000100.timer: maximum frequency is 1220Hz
[ 0.584933] Crashlog allocated RAM at address 0x3f00000
[ 0.591137] workingset: timestamp_bits=30 max_order=14 bucket_order=0
[ 0.605708] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.611355] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 0.629371] io scheduler noop registered
[ 0.633116] io scheduler deadline registered (default)
[ 0.638327] ralink-usb-phy usbphy: invalid resource
[ 0.643673] Serial: 8250/16550 driver, 2 ports, IRQ sharing disabled
[ 0.650977] console [ttyS0] disabled
[ 0.654428] 10000c00.uartlite: ttyS0 at MMIO 0x10000c00 (irq = 20, base_baud = 2500000) is a Palmchip BK-3103
[ 0.664105] console [ttyS0] enabled
[ 0.671135] bootconsole [early0] disabled
[ 0.683501] spi spi0.0: force spi mode3
[ 0.688192] m25p80 spi0.0: s25fl064k (8192 Kbytes)
[ 0.693197] 6 ofpart partitions found on MTD device spi0.0
[ 0.698792] Creating 6 MTD partitions on "spi0.0":
[ 0.703703] 0x000000000000-0x000000020000 : "u-boot"
[ 0.710511] 0x000000020000-0x0000007c0000 : "firmware"
[ 1.713178] 2 tplink-fw partitions found on MTD device firmware
[ 1.719267] 0x000000020000-0x00000016b31c : "kernel"
[ 1.725969] 0x00000016b31c-0x0000007c0000 : "rootfs"
[ 1.732917] mtd: device 3 (rootfs) set to be root filesystem
[ 1.739333] 1 squashfs-split partitions found on MTD device rootfs
[ 1.745662] 0x0000003fb000-0x0000007c0000 : "rootfs_data"
[ 1.752876] 0x0000007c0000-0x0000007d0000 : "config"
[ 1.759826] 0x0000007d0000-0x0000007e0000 : "rom"
[ 1.766443] 0x0000007e0000-0x0000007f0000 : "romfile"
[ 1.773514] 0x0000007f0000-0x000000800000 : "radio"
[ 1.781045] libphy: Fixed MDIO Bus: probed
[ 1.787871] gsw: setting port4 to ephy mode
[ 1.792232] mtk_soc_eth 10100000.ethernet eth0 (uninitialized): port 3 link up (100Mbps/Full duplex)
[ 1.802707] mtk_soc_eth 10100000.ethernet: loaded mt7620 driver
[ 1.809654] mtk_soc_eth 10100000.ethernet eth0: mediatek frame engine at 0xb0100000, irq 5
[ 1.818592] rt2880_wdt 10000120.watchdog: Initialized
[ 1.824973] NET: Registered protocol family 10
[ 1.832550] NET: Registered protocol family 17
[ 1.837150] 8021q: 802.1Q VLAN Support v1.8
[ 1.853533] VFS: Mounted root (squashfs filesystem) readonly on device 31:3.
[ 1.861622] Freeing unused kernel memory: 152K (803fa000 - 80420000)
[ 1.868104] This architecture does not have kernel memory protection.
[ 2.658997] random: fast init done
[ 3.623849] init: Console is alive
[ 3.627539] init: - watchdog -
[ 5.737912] kmodloader: loading kernel modules from /etc/modules-boot.d/
[ 5.953612] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 5.962880] init: - preinit -
[ 7.494494] 8021q: adding VLAN 0 to HW filter on device eth0
[ 8.623275] jffs2: notice: (339) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[ 8.642331] mount_root: switching to jffs2 overlay
[ 8.704772] urandom-seed: Seeding with /etc/urandom.seed
[ 8.837919] procd: - early -
[ 8.841732] procd: - watchdog -
[ 9.000833] procd: cannot set group tty for /dev/ttyS0
[ 9.007309] procd: cannot set group tty for /dev/ttyS1
[ 9.075353] procd: - watchdog -
[ 9.078901] procd: - ubus -
[ 9.264777] procd: - init -
[ 9.836160] kmodloader: loading kernel modules from /etc/modules.d/*
[ 9.852325] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 9.868654] Netfilter messages via NETLINK v0.30.
[ 9.876508] ip_set: protocol 6
[ 9.915182] Loading modules backported from Linux version wt-2017-01-31-0-ge882dff19e7f
[ 9.923435] Backport generated by backports.git backports-20160324-13-g24da7d3c
[ 10.001004] u32 classifier
[ 10.003776] input device check on
[ 10.007575] Actions configured
[ 10.013950] Mirror/redirect action on
[ 10.027821] nf_conntrack version 0.5.0 (1024 buckets, 4096 max)
[ 10.044387] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 10.131821] wireguard: WireGuard 0.0.20170706 loaded. See www.wireguard.io for information.
[ 10.140432] wireguard: Copyright (C) 2015-2017 Jason A. Donenfeld Jason@zx2c4.com. All Rights Reserved.
[ 10.185076] xt_time: kernel timezone is -0000
[ 10.203144] PPP generic driver version 2.4.2
[ 10.210722] NET: Registered protocol family 24
[ 10.236359] rt2800_wmac 10180000.wmac: loaded eeprom from mtd device "radio"
[ 10.243649] ieee80211 phy0: rt2x00_set_rt: Info - RT chipset 6352, rev 0500 detected
[ 10.251580] ieee80211 phy0: rt2x00_set_rf: Info - RF chipset 7620 detected
[ 10.259332] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
[ 10.357836] kmodloader: done loading kernel modules from /etc/modules.d/*
[ 19.174144] 8021q: adding VLAN 0 to HW filter on device eth0
[ 19.200616] br-lan: port 1(eth0.1) entered blocking state
[ 19.206142] br-lan: port 1(eth0.1) entered disabled state
[ 19.212333] device eth0.1 entered promiscuous mode
[ 19.217286] device eth0 entered promiscuous mode
[ 19.258043] br-lan: port 1(eth0.1) entered blocking state
[ 19.263571] br-lan: port 1(eth0.1) entered forwarding state
[ 38.785628] random: crng init done

The issue is most likely this line:
[ 0.454267] mt7620-pci 10140000.pcie: MT7620 PPLL unlock
[ 0.459410] mt7620-pci: probe of 10140000.pcie failed with error -1

It appears the PCI device isn't being initialized properly.