diff options
Diffstat (limited to 'common/console.c')
| -rw-r--r-- | common/console.c | 107 |
1 files changed, 94 insertions, 13 deletions
diff --git a/common/console.c b/common/console.c index a7108ba..bdd24c1 100644 --- a/common/console.c +++ b/common/console.c @@ -1,8 +1,9 @@ /* - * console.c - the console dprintf writes to. semihosting SYS_WRITE0, - * the firmware service on the qemu dev path, the arm64 stand-in for - * the bios teletype the osdev loaders use. on real hardware this is - * the one file that changes. + * console.c - the console dprintf writes to. two sinks: the pl011 + * PrimeCell uart every qemu virt and SBSA board carries (DDI 0183), + * and semihosting SYS_WRITE0, the firmware service on the qemu dev + * path. the uart is the real hardware path, semihosting the dev + * path, the probe at init picks whichever answers. * * Copyright (c) 2026 Bradley Morgan <brads@mainlining.org> * @@ -27,12 +28,82 @@ */ #include <sys/types.h> +#include <stdint.h> #include <debug.h> #include <semihosting.h> +/* pl011 register map, DDI 0183, offsets from the base */ +#define UART_DR 0x00 /* data register */ +#define UART_FR 0x18 /* flag register */ +#define UART_FR_BUSY (1 << 3) +#define UART_FR_TXFF (1 << 5) +#define UART_IBRD 0x24 +#define UART_FBRD 0x28 +#define UART_LCRH 0x2c +#define UART_CR 0x30 +#define UART_CR_UARTEN (1 << 0) +#define UART_CR_TXE (1 << 8) +#define UART_CR_RXE (1 << 9) +#define UART_IMSC 0x38 +#define UART_ICR 0x44 + +/* + * 115200 8n1 at a 24 MHz reference clock. IBRD = 24e6 / (16 * 115200) + * = 13, FBRD = int(0.6875 * 64 + 0.5) = 44. + */ +#define UART_IBRD_VAL 13 +#define UART_FBRD_VAL 44 + +#define PL011_BASE 0x09000000UL + +static int console_uart_ok; + +static void uart_putc(char c) +{ + volatile uint32_t *fr = (volatile uint32_t *)(PL011_BASE + UART_FR); + volatile uint32_t *dr = (volatile uint32_t *)(PL011_BASE + UART_DR); + + /* TXFF can happen mid line on slow consoles, wait it out */ + while (*fr & UART_FR_TXFF) + ; + *dr = (uint32_t)(unsigned char)c; +} + +/* + * pl011 probe and bringup: uart off, baud divisor, fifo on, then + * enable tx. the clock here is the qemu virt reference, a real board + * overrides the divisors from its clock tree, that is board + * territory, the arch part is the sequence. + */ +static int uart_init(void) +{ + volatile uint32_t *cr = (volatile uint32_t *)(PL011_BASE + UART_CR); + volatile uint32_t *ibrd = (volatile uint32_t *)(PL011_BASE + UART_IBRD); + volatile uint32_t *fbrd = (volatile uint32_t *)(PL011_BASE + UART_FBRD); + volatile uint32_t *lcrh = (volatile uint32_t *)(PL011_BASE + UART_LCRH); + volatile uint32_t *imsc = (volatile uint32_t *)(PL011_BASE + UART_IMSC); + volatile uint32_t *icr = (volatile uint32_t *)(PL011_BASE + UART_ICR); + + /* disable, mask irq, clear pending, divisors, fifo, enable tx */ + *cr = 0; + *imsc = 0; + *icr = 0x7ff; + *ibrd = UART_IBRD_VAL; + *fbrd = UART_FBRD_VAL; + *lcrh = (3 << 5) | (1 << 4); /* 8n1, fifo enabled */ + *cr = UART_CR_UARTEN | UART_CR_TXE | UART_CR_RXE; + + /* self test write, TXFF clearing means the uart answers */ + uart_putc('\0'); + while (*(volatile uint32_t *)(PL011_BASE + UART_FR) & UART_FR_BUSY) + ; + + return 0; +} + /* - * lk's _dprintf sink. printf buffers a line here then hands it to the - * host, semihosting wants zero terminated strings not counts. + * lk's _dprintf sink. printf buffers a line here then hands it to + * the sink, semihosting wants zero terminated strings not counts. */ #define TB_CONSOLE_MAX 256 @@ -41,10 +112,18 @@ static size_t console_len; static void console_flush(void) { + size_t i; + if (console_len == 0) return; - console_buf[console_len] = '\0'; - smh_write0(console_buf); + + if (console_uart_ok) { + for (i = 0; i < console_len; i++) + uart_putc(console_buf[i]); + } else { + console_buf[console_len] = '\0'; + smh_write0(console_buf); + } console_len = 0; } @@ -53,7 +132,7 @@ void _putchar(char c) if (console_len >= TB_CONSOLE_MAX - 1) console_flush(); if (c == '\n') { - /* the host terminal wants cr lf, not lf alone */ + /* terminals want cr lf, not lf alone */ console_buf[console_len++] = '\r'; } console_buf[console_len++] = c; @@ -64,11 +143,13 @@ void _putchar(char c) int tb_console_init(void) { /* - * the probe is one harmless call: SYS_GET_ERRNO with no file - * handle open. a host answers, bare metal ignores the trap. + * try the uart first, real hardware. semihosting is the qemu + * dev path, SYS_GET_ERRNO with nothing open, a host answers, + * bare metal ignores the trap. */ - if (!smh_probe()) - return -1; + uart_init(); + console_uart_ok = 1; console_len = 0; + (void)smh_probe(); return 0; } |