minos/arch/riscv/link-d1.ld
Шурупов Илья Викторович 775a02cf3f Add D1/Lichee RV hardware boot and UART input
Bring up minos on the Allwinner D1 (Lichee RV) over FEL/xfel and add
bidirectional UART so the console can read keystrokes, not just print.

D1 / Lichee RV boot:
- riscv arch.c: select UART0 base by -DBOARD_D1 (0x02500000 vs QEMU
  0x10000000) and add a reg-shift abstraction (uart_rd/uart_wr): the D1's
  Synopsys DW-8250 uses 32-bit registers at 4-byte spacing, which is what
  made the first hardware boot silent.
- d1_uart0_init(): gate/deassert UART0 clock, mux PB8/PB9 to UART0, set
  115200 8N1, clear FIFOs, force non-loopback, drain stale RX.
- link-d1.ld: link for DRAM at 0x40000000 (xfel exec target, M-mode).
- Makefile: 'lichee' builds the flat binary; 'run-lichee' loads it via
  xfel (ddr d1 / write / exec).
- arch_name() reports the concrete board.

UART input (all archs):
- arch contract gains arch_uart_getc() and arch_uart_rx_ready(),
  implemented for riscv, x86 (COM1) and arm (Cadence UART).
- console gains getc() and drain_rx().
- kmain() runs an interactive echo loop (seed of the M3 console).

Verified: echo works under QEMU on x86/riscv/arm, and on real D1
hardware (banner once, then live keystroke echo over UART0 @115200).
2026-09-25 21:13:59 +03:00

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/* link-d1.ld (RISC-V, Allwinner D1 / Lichee RV) — bare-metal via xfel.
*
* The D1 boot ROM (FEL) leaves us free to load into DRAM. xfel initialises
* DRAM ('xfel ddr d1') then writes/execs at 0x40000000 (start of the 512MB+
* DDR). 'xfel exec' jumps here still in M-mode, which is what minos expects.
* (QEMU 'virt' uses 0x80000000 instead — see link.ld.) */
OUTPUT_ARCH(riscv)
ENTRY(_start)
SECTIONS
{
. = 0x40000000; /* DRAM base on D1 */
.text : {
KEEP(*(.text.boot)) /* _start must be first */
*(.text .text.*)
}
.rodata : { *(.rodata .rodata.*) }
.data : { *(.data .data.*) }
. = ALIGN(8);
__bss_start = .;
.bss : { *(.bss .bss.*) *(COMMON) }
. = ALIGN(8);
__bss_end = .;
. = ALIGN(16);
. += 0x4000; /* 16 KiB boot stack */
_stack_top = .;
}