i.MX: add an emulation for RNGC

Add an emulation for the RNGC random number generator and the compatible
RNGB variant. These peripherals are included (at least) in imx25 and
imx35 chipsets.

The emulation supports the initial self test, reseeding the prng and
reading random numbers.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 278 insertions, 0 deletions

diff --git a/hw/misc/imx_rngc.c b/hw/misc/imx_rngc.c
new file mode 100644
index 0000000..4c270df
--- /dev/null
+++ b/hw/misc/imx_rngc.c
@@ -0,0 +1,278 @@
+/*
+ * 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/log.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)