diff options
Diffstat (limited to 'drivers/uart.cc')
| -rw-r--r-- | drivers/uart.cc | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/drivers/uart.cc b/drivers/uart.cc new file mode 100644 index 0000000..467b496 --- /dev/null +++ b/drivers/uart.cc @@ -0,0 +1,181 @@ +/* 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); +} + |