mini PCIe serial card (StarTech 2p1s) support

[Philip Tricca]

Hello grub-help,

I've spent the better part of a day trying to get grub to dump output to
a serial device with no luck. From the little experience I do have with
Grub I've never had a problem configuring a serial device so long as
it's "standard serial hardware" like a 8250/16550 UART on the one of the
4 standard I/O ports: 0x3f8, 0x2f8, 0x3e8, 0x2e8. I am however having
trouble getting my add-on PCIe serial hardware (Startek 2s1p) to work.
Likely this is related to the serial ports on this card using I/O ports
on 0xe030 and 0xe020.

I've tested this device with Linux successfully with the kernel
reporting the following in dmesg:

0000:02:00.0: ttyS1 at I/O 0xe030 (irq = 16, base_baud = 115200) is a
ST16650V2

and using the device as expected: I get a kernel log and login from
ttyS1. AFAIK the 16650v2 UART is backward compatible with the 8250. The
difference being the 16650v2 has a 32 byte FIFO.

In the Grub shell I'm able to see the card with lspci:
02:00.0 9710:9912 [0700] Communication controller [PI 02]
        IO space 0 at 0xe030
        32-bit memory space 1 at 0x00000000f7c05000 [non-prefetchable]
        32-bit memory space 5 at 0x00000000f7c04000 [non-prefetchable]
02:00.1 9710:9912 [0700] Communication controller [PI 02]
        IO space 0 at 0xe020
        32-bit memory space 1 at 0x00000000f7c03000 [non-prefetchable]
        32-bit memory space 5 at 0x00000000f7c02000 [non-prefetchable]

I spent some time poking around in the Grub serial code and I ran aross
the include/grub/i386/coreboot/serial.h header (I'm on x84_64 / UEFI)
where the 4 standard serial I/O ports are defined
(GRUB_MACHINE_SERIAL_PORTS). I experimented with adding the I/O port for
my add-on card to this array in an attmpt to get Grub to probe it but
had no luck. Adding the I/O port 0xe030 to the end of the array, as well
as replacing one of the existing 4 entries wasn't successful:

diff --git a/include/grub/i386/coreboot/serial.h
b/include/grub/i386/coreboot/serial.h
index b6819d5..ce79ba0 100644
--- a/include/grub/i386/coreboot/serial.h
+++ b/include/grub/i386/coreboot/serial.h
@@ -19,6 +19,6 @@
#ifndef GRUB_MACHINE_SERIAL_HEADER
#define GRUB_MACHINE_SERIAL_HEADER     1

-#define GRUB_MACHINE_SERIAL_PORTS { 0x3f8, 0x2f8, 0x3e8, 0x2e8 }
+#define GRUB_MACHINE_SERIAL_PORTS { 0xe030, 0x2f8, 0x3e8, 0x2e8 }

#endif

Additional inforation: I'm building Grub from source for the 'x86_64'
target and the 'efi' platform. I'm also linking all of the modules built
into the bootx64.efi image. For testing I'm just copying bootx64.efi to
a GPT/FAT32 USB drive and booting directly from the UEFI shell.

Anyone out there willing to share their experience in the Grub serial
code, specifically with regard to configuring UARTs with weird I/O ports?

Thanks in advance,
Philip