/* $NetBSD: smccc.c,v 1.4 2023/11/07 13:31:26 rin Exp $ */

/*-
 * Copyright (c) 2021 Jared McNeill <jmcneill@invisible.ca>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: smccc.c,v 1.4 2023/11/07 13:31:26 rin Exp $");

#include <sys/param.h>
#include <sys/kernel.h>

#include <arm/arm/psci.h>
#include <arm/arm/smccc.h>

#if defined(__arm__)
#  if defined(__clang__)
#define SMCCC_ARCH_ATTRIBUTE  __attribute__ ((target("armv7ve")))
#  else /* gcc */
#define SMCCC_ARCH_ATTRIBUTE  __attribute__ ((target("arch=armv7ve")))
#  endif
#else
#define SMCCC_ARCH_ATTRIBUTE
#endif

/* Minimum supported PSCI version for SMCCC discovery */
#define PSCI_VERSION_1_0        0x10000

/* Retrieve the implemented version of the SMC Calling Convention. */
#define SMCCC_VERSION           0x80000000

/* True if SMCCC is detected. */
static bool                     smccc_present;

/* SMCCC conduit (SMC or HVC) */
static enum psci_conduit        smccc_conduit = PSCI_CONDUIT_NONE;

/*
 * smccc_probe --
 *
 *      Returns true if SMCCC is supported by platform firmware.
 */
bool
smccc_probe(void)
{
        if (cold && !smccc_present) {
                if (!psci_available() || psci_version() < PSCI_VERSION_1_0) {
                        return false;
                }

                smccc_present = psci_features(SMCCC_VERSION) == PSCI_SUCCESS;
                if (smccc_present) {
                        smccc_conduit = psci_conduit();

                        aprint_debug("SMCCC: Version %#x (%s)\n",
                            smccc_version(),
                            smccc_conduit == PSCI_CONDUIT_SMC ? "SMC" : "HVC");
                }
        }
        return smccc_present;
}

/*
 * smccc_version --
 *
 *      Return the implemented SMCCC version, or a negative error code on failure.
 */
int
smccc_version(void)
{
        return smccc_call(SMCCC_VERSION, 0, 0, 0, 0,
                          NULL, NULL, NULL, NULL);
}

/*
 * smccc_call --
 *
 *      Generic call interface for SMC/HVC calls.
 */
SMCCC_ARCH_ATTRIBUTE int
smccc_call(uint32_t fid,
    register_t arg1, register_t arg2, register_t arg3, register_t arg4,
    register_t *res0, register_t *res1, register_t *res2, register_t *res3)
{
        register_t args[5] = { fid, arg1, arg2, arg3, arg4 };

        register register_t r0 asm ("r0");
        register register_t r1 asm ("r1");
        register register_t r2 asm ("r2");
        register register_t r3 asm ("r3");
        register register_t r4 asm ("r4");

        if (!smccc_present) {
                return SMCCC_NOT_SUPPORTED;
        }

        KASSERT(smccc_conduit != PSCI_CONDUIT_NONE);

        r0 = args[0];
        r1 = args[1];
        r2 = args[2];
        r3 = args[3];
        r4 = args[4];

        if (smccc_conduit == PSCI_CONDUIT_SMC) {
                asm volatile ("smc #0" :
                              "=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3) :
                              "r" (r0), "r" (r1), "r" (r2), "r" (r3), "r" (r4) :
                              "memory");
        } else {
                asm volatile ("hvc #0" :
                              "=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3) :
                              "r" (r0), "r" (r1), "r" (r2), "r" (r3), "r" (r4) :
                              "memory");
        }
        
        if (res0) {
                *res0 = r0;
        }
        if (res1) {
                *res1 = r1;
        }
        if (res2) {
                *res2 = r2;
        }
        if (res3) {
                *res3 = r3;
        }

        return r0;
}