/*
  StarForth — Steady-State Virtual Machine Runtime
  Copyright (c) 2023–2025 Robert A. James. All rights reserved.
  Licensed under the StarForth License, Version 1.0.
 */

/**
 * rpi5_dtb.c - Raspberry Pi 5 (BCM2712) devicetree-based peripheral
 * discovery (FABRIC-3.md §IV.3, 2026-09-04).
 *
 * Confirmed directly against `bcm2712.dtsi` (raspberrypi/linux,
 * rpi-6.12.y) before writing this, not assumed:
 *
 *   soc: soc@107c000000 {
 *       compatible = "simple-bus";
 *       ranges = <0x0 0x10 0x0 0x80000000>;
 *       #address-cells = <1>;
 *       #size-cells = <1>;
 *       ...
 *       uart10: serial@7d001000 {
 *           compatible = "arm,pl011", "arm,primecell";
 *           reg = <0x7d001000 0x200>;
 *       };
 *       mailbox: mailbox@7c013880 {
 *           compatible = "brcm,bcm2835-mbox";
 *           reg = <0x7c013880 0x40>;
 *       };
 *   };
 *
 * Every peripheral this file cares about lives under this one "soc"
 * node, which applies exactly one translation to every child `reg`
 * value: child address 0 maps to parent (CPU-physical) address
 * 0x10_0000_0000 (`ranges`'s own `<0x0 0x10 0x0 ...>` — child cell 0,
 * parent cells `0x10 0x0`, i.e. `0x10 << 32`). The child side's own
 * `#address-cells = <1>` confirms each `reg` value's first cell is the
 * whole child address (32-bit, no cell-splitting needed) before adding
 * the offset. `fdt.c`'s reader deliberately does not parse `ranges`
 * generally (it is "not a general devicetree library," per its own
 * header comment) — this one, fixed, SoC-wide offset is applied here
 * by name instead, since it is a single known hardware fact, not a
 * general mechanism this codebase needs elsewhere yet.
 */

#include "starkernel/rpi5_dtb.h"
#include "starkernel/fdt.h"

/* soc@107c000000's own `ranges` offset -- see this file's own doc
 * comment above for where it was confirmed. */
#define BCM2712_SOC_RANGES_OFFSET 0x1000000000ULL

/**
 * @brief Read a devicetree `reg` property's first cell as big-endian.
 *
 * `fdt.c` keeps its own `be32()` helper file-local (freestanding, no
 * shared byte-swap utility to reuse) -- duplicated here rather than
 * exposing it, same "a few lines is simpler than a new shared
 * dependency" precedent `tools/pkcs8_ed25519.c` already set in this
 * codebase.
 */
static uint32_t reg_first_cell_be32(const unsigned char* b)
{
    return ((uint32_t) b[0] << 24) | ((uint32_t) b[1] << 16) |
           ((uint32_t) b[2] << 8) | (uint32_t) b[3];
}

/**
 * @brief Find @p compatible's node, read its `reg` base address, and
 * apply the one fixed BCM2712 `soc`-node translation offset.
 */
static uint64_t rpi5_peripheral_base(const void* dtb, const char* compatible)
{
    const void* node;
    const void* val;
    uint32_t len;

    node = fdt_find_node_by_compatible(dtb, compatible);
    if (!node) return 0;

    val = fdt_find_prop_in_node(dtb, node, "reg", &len);
    if (!val || len < 4) return 0;

    return BCM2712_SOC_RANGES_OFFSET + reg_first_cell_be32((const unsigned char*) val);
}

uint64_t rpi5_uart_base(const void* dtb)
{
    return rpi5_peripheral_base(dtb, "arm,pl011");
}

uint64_t rpi5_mailbox_base(const void* dtb)
{
    return rpi5_peripheral_base(dtb, "brcm,bcm2835-mbox");
}