ramdetect.c

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/* SPDX-License-Identifier: GPL-2.0-or-later */
 
#include <types.h>
#include <device/mmio.h>
#include <ramdetect.h>
#include <arch/exception.h>
#include <arch/transition.h>
 
static enum {
        ABORT_CHECKER_NOT_TRIGGERED,
        ABORT_CHECKER_TRIGGERED,
} abort_state = ABORT_CHECKER_NOT_TRIGGERED;
 
static int abort_checker(struct exc_state *state, uint64_t vector_id)
{
        if (raw_read_esr_el3() >> 26 != 0x25)
                return EXC_RET_IGNORED; /* Not a data abort. */
 
        abort_state = ABORT_CHECKER_TRIGGERED;
        state->elx.elr += sizeof(uint32_t); /* Jump over faulting instruction. */
        raw_write_elr_el3(state->elx.elr);
        return EXC_RET_HANDLED;
}
 
static struct exception_handler sync_el0 = {.handler = &abort_checker};
 
int probe_mb(const uintptr_t dram_start, const uintptr_t size)
{
        uintptr_t addr = dram_start + (size * MiB) - sizeof(uint32_t);
        void *ptr = (void *)addr;
 
        abort_state = ABORT_CHECKER_NOT_TRIGGERED;
        exception_handler_register(EXC_VID_CUR_SP_EL0_SYNC, &sync_el0);
        read32(ptr);
        exception_handler_unregister(EXC_VID_CUR_SP_EL0_SYNC, &sync_el0);
        return abort_state == ABORT_CHECKER_NOT_TRIGGERED;
}