[Bug 237055] Ampere eMAG compatibility

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237055

            Bug ID: 237055
           Summary: Ampere eMAG compatibility
           Product: Base System
           Version: CURRENT
          Hardware: arm64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: arm
          Assignee: freebsd-arm at FreeBSD.org
          Reporter: greg at unrelenting.technology

Created attachment 203420
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=203420&action=edit
emag.multiuser.dmesg

Sooo, now that Packet has Ampere eMAG instances (c2.large.arm), of course
someone had to try FreeBSD and of course it's me… :D

tl;dr I managed to boot to multiuser with some hacks, but PCIe is busted, needs
support for more ACPI stuff. Verbose boot log is attached, I'll attach ACPI
tables and stuff too.

---

0. Installation

I used an Ubuntu 18.04 instance, rerooted to a ramdisk ( using the method I
described in https://community.online.net/t/freebsd-on-arm64/6678 ), resized
the Linux partition, added a new one, loop mounted a memstick image, dd'd it
onto the new partition, copied loader_lua.efi to the EFI partition, added a
GRUB entry to chainload that:

menuentry 'FreeBSD' {
  load_video
  insmod part_gpt
  insmod chain
  set root='hd0,gpt1'
  chainloader /EFI/BSD/loader_lua.efi
}

and used https://github.com/mkatiyar/fuse-ufs2 to modify the UFS partition from
Linux. (As long as you don't copy files from the UFS partition *to itself*, it
works fine lol. If you do that, it gets stuck in a 100% cpu loop)

1. Console

https://reviews.freebsd.org/D19507 is needed for any UART output now that one
part from there (not using the hardcoded regshift) has landed. Now we need to
hardcode it again but only for PL011.

But that's not all. For some reason, I'm not seeing userspace output
(/dev/console) even though the ACPI node for the console was picked up:

uart0: <PrimeCell UART (PL011)> iomem 0x12600000-0x12600fff irq 1 on acpi0
uart0: console (115200,n,8,1)
uart0: fast interrupt
uart0: PPS capture mode: DCD

2. Weird early memory access crashes

EFI runtime support (specifically, enumerating efirtc) crashed in efi_call() at
efi_get_time+0x50. I disabled `options EFIRT`.

Then ACPI crashed in AcpiExSystemMemorySpaceHandler when reading:

  exfield-0369 ExReadDataFromField   : FieldRead [TO]:   Obj
0xfffffd0010b41980, Type 11, Buf 0xfffffd0010b62b10, ByteLen 8
  exfield-0372 ExReadDataFromField   : FieldRead [FROM]: BitLen 1, BitOff 6,
ByteOff 0
  exfldio-0395 ExAccessRegion        : [READ] Region [SystemMemory:0], Width 4,
ByteBase 0, Offset 0 at 000000001F10C004

I patched DSDT, removing OperationRegion CLKE from Device AHBC. The only thing
that used this was Method _INI for Device I2C4, so I removed the body of that
method as well.
Who cares about i2c on a server :) that allowed booting to proceed.

3. PCIe is screwed up

There's this interesting message for all PCI bridges:

pcib0: bus end mismatch! expected 255 found 31.

And some more interesting messages (for the last couple pcib's also with "I/O
port window" and "bar .. failed to allocate"):

pcib0: rman_reserve_resource: start=0x30000000, end=0x301fffff, count=0x200000
pcib0: pci_host_generic_core_alloc_resource FAIL: type=3, rid=32,
start=0000000030000000, end=00000000301fffff, count=0000000000200000, flags=0
pcib1: failed to allocate initial memory window: 0x30000000-0x301fffff
pcib0: rman_reserve_resource: start=0x14080000000, end=0x14084ffffff,
count=0x5000000

PCIe cards actually don't work when these messages are present:

mlx5_core0: <mlx5_core> mem 0x14082000000-0x14083ffffff at device 0.0 on pci1
mlx5_core0: ERR: Failed mapping initialization segment, aborting

Looking at Ampere's page
https://github.com/AmpereComputing/ampere-centos-kernel/wiki/Ampere-CentOS-Kernel-wiki

it seems like Linux needed to ACPI _DMA objects and IORT named components:

https://github.com/torvalds/linux/commit/4f0450af530e62b0217522cab4803b5a65dccc46
https://github.com/torvalds/linux/commit/c04ac679c6b86e4e36fbb675c6c061b4091f5810
https://github.com/torvalds/linux/commit/7ad4263980826e8b02e121af22f4f4c9103fe86d
https://github.com/torvalds/linux/commit/10d8ab2c15b9ef2f46c35e7c36781399d6f2cc82

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