[FS#623] ar71xx: RB750UPr2: No serial console

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - João Chainho (joaochainho) 

Attached to Project - LEDE Project
Summary - ar71xx: RB750UPr2: No serial console
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Hello, 
The serial console isn't working on MikroTik RB750UPr2 (NOR flash) (normal boot). Netboot is fine though. Notice **no-uart** in the kernel command line args.
Tested with recent snapshots (r3607-d49ddcd, r3617-f9da623)
 
**Netboot**

[    0.000000] Linux version 4.4.52 (buildbot at builds) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3607-d49ddcd) ) #0 Wed Mar 8 18:06:04 2017
[    0.000000] bootconsole [early0] enabled
...
[    0.000000] Kernel command line: no-uart no-nand parts=1 boot_part_size=16777216 gpio=8525375 HZ=325000000 mem=64M kmac=E4:8D:8C:99:18:31 board=750-hb hw_opt=0008400D boot=0 mlc=8 console=ttyS0,115200 rootfstype=squashfs noinitrd
...
[    0.125208] MIPS: machine is MikroTik RouterBOARD 750UP r2
...
[    2.957103] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[    2.967151] console [ttyS0] disabled
[    2.991360] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 1562500) is a 16550A
[    3.001161] console [ttyS0] enabled
[    3.001161] console [ttyS0] enabled
[    3.008713] bootconsole [early0] disabled
[    3.008713] bootconsole [early0] disabled
[    3.023066] m25p80 spi0.0: found w25q128, expected m25p80
[    3.028744] m25p80 spi0.0: w25q128 (16384 Kbytes)
[    3.033619] Creating 6 MTD partitions on "spi0.0":
[    3.038569] 0x000000000000-0x00000000e000 : "routerboot"
[    3.046718] 0x00000000e000-0x00000000f000 : "hard_config"
[    3.054081] 0x00000000f000-0x000000010000 : "bios"
[    3.060744] 0x000000010000-0x00000001f000 : "routerboot2"
[    3.068174] 0x00000001f000-0x000000020000 : "soft_config"
[    3.075587] 0x000000020000-0x000001000000 : "firmware"



**Normal boot**

[    0.000000] Linux version 4.4.52 (buildbot at buildslave) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3617-f9da623) ) #0 Fri Mar 10 00:23:50 2017
[    0.000000] bootconsole [early0] enabled
...
[    0.000000] Kernel command line: no-uart no-nand parts=1 boot_part_size=16777216 gpio=0 HZ=325000000 mem=64M kmac=E4:8D:8C:99:18:31 board=750-hb Board=750-hb ver=3.36 hw_opt=0008400D boot=1 mlc=10 console=ttyS0,115200 rootfstype=squashfs noinitrd
...
[    0.125275] MIPS: machine is MikroTik RouterBOARD 750UP r2
...
[    0.696259] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[    0.706324] console [ttyS0] disabled
[    0.730536] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 1562500) is a 16550A
[    0.740339] console [ttyS0] enabled
[    0.747890] bootconsole [early0] disabled
[    0.762167] m25p80 spi0.0: found w25q128, expected m25p80
[    0.767840] m25p80 spi0.0: w25q128 (16384 Kbytes)
[    0.772706] Creating 6 MTD partitions on "spi0.0":
[    0.777667] 0x000000000000-0x00000000e000 : "routerboot"
[    0.785835] 0x00000000e000-0x00000000f000 : "hard_config"
[    0.793114] 0x00000000f000-0x000000010000 : "bios"
[    0.799850] 0x000000010000-0x00000001f000 : "routerboot2"
[    0.807243] 0x00000001f000-0x000000020000 : "soft_config"
[    0.814630] 0x000000020000-0x000001000000 : "firmware"
[    0.865054] 2 minor-fw partitions found on MTD device firmware
[    0.871104] 0x000000020000-0x0000001a0000 : "kernel"
[    0.877734] 0x0000001a0000-0x000001000000 : "rootfs"
[    0.884687] mtd: device 7 (rootfs) set to be root filesystem
[    0.890584] 1 squashfs-split partitions found on MTD device rootfs
[    0.897035] 0x000000390000-0x000001000000 : "rootfs_data"


BTW the serial console is working fine on RB750UP (NAND flash) (normal boot).

[    0.000000] Kernel command line: parts=1 boot_part_size=4194304 gpio=790343 HZ=200000000 mem=32M kmac=D4:CA:6D:91:86:F1 board=750i Board=750i ver=3.33 hw_opt=0000000D boot=1 mlc=10 console=ttyS0,115200 rootfstype=squashfs noinitrd



More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=623