Use db_rint() in sfuart(4)

This lets me enter ddb(4) even when the riscv64 machines I manage get
unusable because of NFS.

Suggested by miod@, ok miod@ kettenis@

constify struct cfattach

Using suser() instead of doing it manually.

ok patrick@

Make sure we program the baud rate divisor register. Without this,
opening the tty corresponding to a non-console device will hang the
machine.

ok deraadt@

Clean this up a bit. Use register names that match the documentation, and
fix some register number. Drop reading the Interrupt Pending register
in the interrupt handler as this was actually reading the Interrupt Enable
register and the bits that were checked were always true. Fix bogus
code in sfuartcnputc() and simplyfy sfuartcngetc(). Throw in some
style fixes for good measure.

Serial driver for SiFive Unmatched (U74) based on dev/fdt/amluart.c
console input and output working, userland input and output at least
partially working.
'commit that driver, further improvements can happen in-tree' deraadt@

constify struct cfattach

Using suser() instead of doing it manually.

ok patrick@

Make sure we program the baud rate divisor register. Without this,
opening the tty corresponding to a non-console device will hang the
machine.

ok deraadt@

Clean this up a bit. Use register names that match the documentation, and
fix some register number. Drop reading the Interrupt Pending register
in the interrupt handler as this was actually reading the Interrupt Enable
register and the bits that were checked were always true. Fix bogus
code in sfuartcnputc() and simplyfy sfuartcngetc(). Throw in some
style fixes for good measure.

Serial driver for SiFive Unmatched (U74) based on dev/fdt/amluart.c
console input and output working, userland input and output at least
partially working.
'commit that driver, further improvements can happen in-tree' deraadt@

Using suser() instead of doing it manually.

ok patrick@

Make sure we program the baud rate divisor register. Without this,
opening the tty corresponding to a non-console device will hang the
machine.

ok deraadt@

Clean this up a bit. Use register names that match the documentation, and
fix some register number. Drop reading the Interrupt Pending register
in the interrupt handler as this was actually reading the Interrupt Enable
register and the bits that were checked were always true. Fix bogus
code in sfuartcnputc() and simplyfy sfuartcngetc(). Throw in some
style fixes for good measure.

Serial driver for SiFive Unmatched (U74) based on dev/fdt/amluart.c
console input and output working, userland input and output at least
partially working.
'commit that driver, further improvements can happen in-tree' deraadt@

Make sure we program the baud rate divisor register. Without this,
opening the tty corresponding to a non-console device will hang the
machine.

ok deraadt@

Clean this up a bit. Use register names that match the documentation, and
fix some register number. Drop reading the Interrupt Pending register
in the interrupt handler as this was actually reading the Interrupt Enable
register and the bits that were checked were always true. Fix bogus
code in sfuartcnputc() and simplyfy sfuartcngetc(). Throw in some
style fixes for good measure.

Serial driver for SiFive Unmatched (U74) based on dev/fdt/amluart.c
console input and output working, userland input and output at least
partially working.
'commit that driver, further improvements can happen in-tree' deraadt@

Clean this up a bit. Use register names that match the documentation, and
fix some register number. Drop reading the Interrupt Pending register
in the interrupt handler as this was actually reading the Interrupt Enable
register and the bits that were checked were always true. Fix bogus
code in sfuartcnputc() and simplyfy sfuartcngetc(). Throw in some
style fixes for good measure.

Serial driver for SiFive Unmatched (U74) based on dev/fdt/amluart.c
console input and output working, userland input and output at least
partially working.
'commit that driver, further improvements can happen in-tree' deraadt@