Changeset 98a935e in mainline for kernel/arch/amd64/src/amd64.c

Timestamp:

2021-08-04T19:30:39Z (3 years ago)

Author:

jxsvoboda <5887334+jxsvoboda@…>

Branches:

master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

8bb0af7f, f05edcb

Parents:

31e15be

git-author:

Marek Benc <dusxmt@…> (2021-06-23 20:56:38)

git-committer:

jxsvoboda <5887334+jxsvoboda@…> (2021-08-04 19:30:39)

Message:

Configure NS16550 transmission format settings on initialization on PCs.

Currently, the NS116550 serial line controller is left with its
settings as it was left by the boot firmware and/or bootloader.
On my computer, this was an invalid configuration, and it left me
with a really slow booting system, since each output character
had to go through the full timeout loop in ns16550_sendb().

This patch adds the necessary bit and register descriptions to configure
the baud rate and transmission settings, as well as configuring them on
post-SMP initialization on ia32 and amd64, currently with values matching
the ns8250 userspace character device driver (38400 baud, 8-bit words,
2 stop bits, no parity).

This could perhaps be changed to be adjustable with a kernel command-line
argument, or through the configuration system.

This change does not affect emulators, since those largely ignore these
settings.

File:

• kernel/arch/amd64/src/amd64.c (modified) (1 diff)

kernel/arch/amd64/src/amd64.c

@@ -224 +224 @@
             ns16550_out_ptr);
         if (ns16550_instance) {
+                ns16550_format_set(ns16550_instance, 38400,
+                    LCR_PARITY_NONE | LCR_STOP_BIT_TWO | LCR_WORD_LEN_8);
 #ifdef CONFIG_NS16550
                 srln_instance_t *srln_instance = srln_init();