/*
* Freescale i.MX RNGC emulation
*
* Copyright (C) 2020 Martin Kaiser <martin@kaiser.cx>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
* This driver provides the minimum functionality to initialize and seed
* an rngc and to read random numbers. The rngb that is found in imx25
* chipsets is also supported.
*/
#include "qemu/osdep.h"
#include "qemu/main-loop.h"
#include "qemu/module.h"
#include "qemu/guest-random.h"
#include "hw/irq.h"
#include "hw/misc/imx_rngc.h"
#include "migration/vmstate.h"
#define RNGC_NAME "i.MX RNGC"
#define RNGC_VER_ID 0x00
#define RNGC_COMMAND 0x04
#define RNGC_CONTROL 0x08
#define RNGC_STATUS 0x0C
#define RNGC_FIFO 0x14
/* These version info are reported by the rngb in an imx258 chip. */
#define RNG_TYPE_RNGB 0x1
#define V_MAJ 0x2
#define V_MIN 0x40
#define RNGC_CMD_BIT_SW_RST 0x40
#define RNGC_CMD_BIT_CLR_ERR 0x20
#define RNGC_CMD_BIT_CLR_INT 0x10
#define RNGC_CMD_BIT_SEED 0x02
#define RNGC_CMD_BIT_SELF_TEST 0x01
#define RNGC_CTRL_BIT_MASK_ERR 0x40
#define RNGC_CTRL_BIT_MASK_DONE 0x20
#define RNGC_CTRL_BIT_AUTO_SEED 0x10
/* the current status for self-test and seed operations */
#define OP_IDLE 0
#define OP_RUN 1
#define OP_DONE 2
static uint64_t imx_rngc_read(void *opaque, hwaddr offset, unsigned size)
{
IMXRNGCState *s = IMX_RNGC(opaque);
uint64_t val = 0;
switch (offset) {
case RNGC_VER_ID:
val |= RNG_TYPE_RNGB << 28 | V_MAJ << 8 | V_MIN;
break;
case RNGC_COMMAND:
if (s->op_seed == OP_RUN) {
val |= RNGC_CMD_BIT_SEED;
}
if (s->op_self_test == OP_RUN) {
val |= RNGC_CMD_BIT_SELF_TEST;
}
break;
case RNGC_CONTROL:
/*
* The CTL_ACC and VERIF_MODE bits are not supported yet.
* They read as 0.
*/
val |= s->mask;
if (s->auto_seed) {
val |= RNGC_CTRL_BIT_AUTO_SEED;
}
/*
* We don't have an internal fifo like the real hardware.
* There's no need for strategy to handle fifo underflows.
* We return the FIFO_UFLOW_RESPONSE bits as 0.
*/
break;
case RNGC_STATUS:
/*
* We never report any statistics test or self-test errors or any
* other errors. STAT_TEST_PF, ST_PF and ERROR are always 0.
*/
/*
* We don't have an internal fifo, see above. Therefore, we
* report back the default fifo size (5 32-bit words) and
* indicate that our fifo is always full.
*/
val |= 5 << 12 | 5 << 8;
/* We always have a new seed available. */
val |= 1 << 6;
if (s->op_seed == OP_DONE) {
val |= 1 << 5;
}
if (s->op_self_test == OP_DONE) {
val |= 1 << 4;
}
if (s->op_seed == OP_RUN || s->op_self_test == OP_RUN) {
/*
* We're busy if self-test is running or if we're
* seeding the prng.
*/
val |= 1 << 1;
} else {
/*
* We're ready to provide secure random numbers whenever
* we're not busy.
*/
val |= 1;
}
break;
case RNGC_FIFO:
qemu_guest_getrandom_nofail(&val, sizeof(val));
break;
}
return val;
}
static void imx_rngc_do_reset(IMXRNGCState *s)
{
s->op_self_test = OP_IDLE;
s->op_seed = OP_IDLE;
s->mask = 0;
s->auto_seed = false;
}
static void imx_rngc_write(void *opaque, hwaddr offset, uint64_t value,
unsigned size)
{
IMXRNGCState *s = IMX_RNGC(opaque);
switch (offset) {
case RNGC_COMMAND:
if (value & RNGC_CMD_BIT_SW_RST) {
imx_rngc_do_reset(s);
}
/*
* For now, both CLR_ERR and CLR_INT clear the interrupt. We
* don't report any errors yet.
*/
if (value & (RNGC_CMD_BIT_CLR_ERR | RNGC_CMD_BIT_CLR_INT)) {
qemu_irq_lower(s->irq);
}
if (value & RNGC_CMD_BIT_SEED) {
s->op_seed = OP_RUN;
qemu_bh_schedule(s->seed_bh);
}
if (value & RNGC_CMD_BIT_SELF_TEST) {
s->op_self_test = OP_RUN;
qemu_bh_schedule(s->self_test_bh);
}
break;
case RNGC_CONTROL:
/*
* The CTL_ACC and VERIF_MODE bits are not supported yet.
* We ignore them if they're set by the caller.
*/
if (value & RNGC_CTRL_BIT_MASK_ERR) {
s->mask |= RNGC_CTRL_BIT_MASK_ERR;
} else {
s->mask &= ~RNGC_CTRL_BIT_MASK_ERR;
}
if (value & RNGC_CTRL_BIT_MASK_DONE) {
s->mask |= RNGC_CTRL_BIT_MASK_DONE;
} else {
s->mask &= ~RNGC_CTRL_BIT_MASK_DONE;
}
if (value & RNGC_CTRL_BIT_AUTO_SEED) {
s->auto_seed = true;
} else {
s->auto_seed = false;
}
break;
}
}
static const MemoryRegionOps imx_rngc_ops = {
.read = imx_rngc_read,
.write = imx_rngc_write,
.endianness = DEVICE_NATIVE_ENDIAN,
};
static void imx_rngc_self_test(void *opaque)
{
IMXRNGCState *s = IMX_RNGC(opaque);
s->op_self_test = OP_DONE;
if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
qemu_irq_raise(s->irq);
}
}
static void imx_rngc_seed(void *opaque)
{
IMXRNGCState *s = IMX_RNGC(opaque);
s->op_seed = OP_DONE;
if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
qemu_irq_raise(s->irq);
}
}
static void imx_rngc_realize(DeviceState *dev, Error **errp)
{
IMXRNGCState *s = IMX_RNGC(dev);
SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
memory_region_init_io(&s->iomem, OBJECT(s), &imx_rngc_ops, s,
TYPE_IMX_RNGC, 0x1000);
sysbus_init_mmio(sbd, &s->iomem);
sysbus_init_irq(sbd, &s->irq);
s->self_test_bh = qemu_bh_new(imx_rngc_self_test, s);
s->seed_bh = qemu_bh_new(imx_rngc_seed, s);
}
static void imx_rngc_reset(DeviceState *dev)
{
IMXRNGCState *s = IMX_RNGC(dev);
imx_rngc_do_reset(s);
}
static const VMStateDescription vmstate_imx_rngc = {
.name = RNGC_NAME,
.version_id = 1,
.minimum_version_id = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT8(op_self_test, IMXRNGCState),
VMSTATE_UINT8(op_seed, IMXRNGCState),
VMSTATE_UINT8(mask, IMXRNGCState),
VMSTATE_BOOL(auto_seed, IMXRNGCState),
VMSTATE_END_OF_LIST()
}
};
static void imx_rngc_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = imx_rngc_realize;
dc->reset = imx_rngc_reset;
dc->desc = RNGC_NAME,
dc->vmsd = &vmstate_imx_rngc;
}
static const TypeInfo imx_rngc_info = {
.name = TYPE_IMX_RNGC,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(IMXRNGCState),
.class_init = imx_rngc_class_init,
};
static void imx_rngc_register_types(void)
{
type_register_static(&imx_rngc_info);
}
type_init(imx_rngc_register_types)
