Snuffleupagus interface for f00d

readas.c

/*
 * Copyright (C) 2021-2022 skgleba
 *
 * This software may be modified and distributed under the terms
 * of the MIT license.
 */

#define READAS_REG 0xE0020040 // readas32 device

#define RAS_DEV_S 0 // default secure
#define RAS_MODE_WRITE 0b1 // write mode
#define RAS_DEV_UNK 0b10 // masks DRAM and DRAM regs, from arm bus
#define RAS_DEV_NS 0b100 // non-secure

// below options only apply to write mode and some offsets in read mode
#define RAS_B0 0b1000
#define RAS_B1 0b10000 // or RAS_NOALIGN in incompatible read offsets
#define RAS_B2 0b100000
#define RAS_B3 0b1000000
#define RAS_32 (RAS_B0 | RAS_B1 | RAS_B2 | RAS_B3)

typedef struct {
    unsigned int addr;
    unsigned int resp;
    unsigned int mode;
} __attribute__((packed)) e002_readas32;


static volatile e002_readas32* const READAS32 = (void*)READAS_REG;

static u32_t readAs(u32_t addr, u32_t mode) {
    READAS32->addr = addr;
    READAS32->resp = 0xDEADBABE;
    READAS32->mode = mode;
    
    while (READAS32->resp == 0xDEADBABE) {} // wait until RAS replies
    
    return READAS32->resp;
}

static void writeAs(u32_t addr, u32_t data, u32_t mode) {
    READAS32->addr = addr;
    READAS32->resp = data;
    READAS32->mode = mode | RAS_MODE_WRITE;
}