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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
/*
* uart.cc — 16550a UART driver + console registry
*
* Two roles:
* 1. Early console: early_putc() for pre-init output (panic, kprintf)
* 2. Runtime console: struct console registered with register_console().
* klog/printk route through console_write_all() → uart_console_write().
*
* The console registry is a simple linked list of struct console.
* console_write_all() iterates the list and calls each console's write().
* If no console is registered, it falls back to early_putc().
*
* Reference: Linux kernel/printk/printk.c, drivers/tty/serial/8250/
*/
#include <lume/console.h>
#include <lume/fdt.h>
#include <lume/vmm.h>
#include <lume/addr.h>
#include <arch/config.h>
/* ================================================================== */
/* UART state */
/* ================================================================== */
static uint64 g_uart_pa = 0;
static uint64 g_uart_size = 0;
static bool g_runtime_mapping_ready = false;
static bool g_mmu_enabled = false;
/* ================================================================== */
/* Early console (Phase 1) */
/* ================================================================== */
extern "C" void console_set_mmu_enabled() {
g_mmu_enabled = true;
}
extern "C" void early_putc(char c) {
if (!g_uart_pa) return;
/*
* Before vmm_init() activates the final page table, UART MMIO is only
* reachable via the bootstrap fixed direct map from entry.S.
* After activation, switch to the runtime (possibly KASLR-slid) base.
*/
uint64 uart_va = 0;
if (g_runtime_mapping_ready) {
uart_va = pa_to_va(phys_addr(g_uart_pa)).raw;
} else if (!g_mmu_enabled) {
uart_va = g_uart_pa;
} else {
uart_va = boot_pa_to_va(phys_addr(g_uart_pa)).raw;
}
volatile auto* uart = reinterpret_cast<volatile uint8*>(uart_va);
*uart = static_cast<uint8>(c);
}
extern "C" void early_puts(const char* s) {
while (*s) early_putc(*s++);
}
void console_early_init(uint64 fdt_paddr) {
uint64 pa = 0;
uint64 size = 0;
FdtManager::early_scan_uart(fdt_paddr, &pa, &size);
if (pa != 0) {
g_uart_pa = pa;
if (size != 0) g_uart_size = size;
}
}
void console_init() {
/*
* Once vmm_init() activates the new page table, the 1GB identity map is dropped.
* The UART must be explicitly registered into the active page table.
*/
if (g_uart_pa != 0 && g_uart_size != 0) {
vmm_map_kernel_mmio(g_uart_pa, g_uart_size);
}
}
void console_use_runtime_mapping() {
g_runtime_mapping_ready = true;
}
/* ================================================================== */
/* Console registry (Phase 2) — linked list of struct console */
/* ================================================================== */
static list_node g_console_list;
static bool g_console_list_init = false;
void register_console(console* con)
{
if (!con) return;
if (!g_console_list_init) {
g_console_list.init();
g_console_list_init = true;
}
con->flags |= CON_ENABLED;
con->list.init();
/* Insert at tail */
list_add_tail(&con->list, &g_console_list);
}
void unregister_console(console* con)
{
if (!con) return;
list_del_init(&con->list);
con->flags &= ~CON_ENABLED;
}
bool console_drivers_registered()
{
if (!g_console_list_init) return false;
return !list_empty(&g_console_list);
}
void console_write_all(const char* s, int count)
{
if (g_console_list_init && !list_empty(&g_console_list)) {
list_node* pos;
list_for_each(pos, &g_console_list) {
auto* con = container_of(pos, console, list);
if ((con->flags & CON_ENABLED) && con->write) {
con->write(con, s, static_cast<unsigned int>(count));
}
}
} else {
/* Fallback: direct early_putc (pre-registration) */
for (int i = 0; i < count; i++) {
early_putc(s[i]);
}
}
}
/* ================================================================== */
/* UART console driver */
/* ================================================================== */
static void uart_console_write(console* /*con*/, const char* s, unsigned int count)
{
for (unsigned int i = 0; i < count; i++) {
if (s[i] == '\n') {
early_putc('\r');
}
early_putc(s[i]);
}
}
/*
* uart_console must be initialized at RUNTIME, not with static
* aggregate initializers. Reason: KASLR self-relocation processes
* .rela.dyn entries for simple pointer variables, but may not cover
* function pointer fields inside static aggregate initializers.
* A static `{ .write = uart_console_write }` would store the
* pre-relocation address, causing a crash when called.
*/
static console uart_console;
void uart_register_console()
{
uart_console.name = "ttyS";
uart_console.write = uart_console_write;
uart_console.setup = nullptr;
uart_console.flags = CON_ENABLED | CON_BOOT;
uart_console.index = 0;
uart_console.data = nullptr;
uart_console.list.init();
register_console(&uart_console);
}
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