duplicate consoles on riscv64

[Dimitri John Ledkov]

When booting on SiFive boards, there are two gettys launched on the same console.

There is sifive serial console which is the active/only physical console.

But also, there is serial console exposed over legacy opensbi extension; which in linux kernel is implemented as hvc0 console, which systemd starts getty for.

The issue is that the both consoles are actually the same one.

Thus some other distros chose to hard-code disable hvc0 console on riscv64.

But given that the legacy sbi serial console extension will eventually go away, it makes sense to disable that in the kernel out right.

By setting:

+# CONFIG_RISCV_SBI_V01 is not set
+# CONFIG_SERIAL_EARLYCON_RISCV_SBI is not set
+# CONFIG_HVC_RISCV_SBI is not set

This way sifive0 console will be discovered and used automatically; ditto earlyprintk without needing to specify sbi or explicitely set sifive0 console.

This will also improve UX experience with just a single getty on the serial connection.

Before the patch is applied:
# ls /run/systemd/generator/getty.target.wants/
<email address hidden> <email address hidden>

After the patch is applied:
$ sudo ls /run/systemd/generator/getty.target.wants/
<email address hidden>

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-riscv - 5.11.0-1007.7

---------------
linux-riscv (5.11.0-1007.7) hirsute; urgency=medium

  [ Ubuntu: 5.11.0-16.17 ]

  * hirsute beta desktop AMD64 ISO kernel panic on boot when booting using UEFI
    (LP: #1922403)
    - SAUCE: efifb: Check efifb_pci_dev before using it

 -- Seth Forshee <email address hidden> Wed, 14 Apr 2021 14:53:29 -0500