hw/misc/imx_rngc.c

   1 /*
   2  * Freescale i.MX RNGC emulation
   3  *
   4  * Copyright (C) 2020 Martin Kaiser <martin@kaiser.cx>
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2 or later.
   7  * See the COPYING file in the top-level directory.
   8  *
   9  * This driver provides the minimum functionality to initialize and seed
  10  * an rngc and to read random numbers. The rngb that is found in imx25
  11  * chipsets is also supported.
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qemu/main-loop.h"
  16 #include "qemu/module.h"
  17 #include "qemu/guest-random.h"
  18 #include "hw/irq.h"
  19 #include "hw/misc/imx_rngc.h"
  20 #include "migration/vmstate.h"
  21
  22 #define RNGC_NAME "i.MX RNGC"
  23
  24 #define RNGC_VER_ID  0x00
  25 #define RNGC_COMMAND 0x04
  26 #define RNGC_CONTROL 0x08
  27 #define RNGC_STATUS  0x0C
  28 #define RNGC_FIFO    0x14
  29
  30 /* These version info are reported by the rngb in an imx258 chip. */
  31 #define RNG_TYPE_RNGB 0x1
  32 #define V_MAJ 0x2
  33 #define V_MIN 0x40
  34
  35 #define RNGC_CMD_BIT_SW_RST    0x40
  36 #define RNGC_CMD_BIT_CLR_ERR   0x20
  37 #define RNGC_CMD_BIT_CLR_INT   0x10
  38 #define RNGC_CMD_BIT_SEED      0x02
  39 #define RNGC_CMD_BIT_SELF_TEST 0x01
  40
  41 #define RNGC_CTRL_BIT_MASK_ERR  0x40
  42 #define RNGC_CTRL_BIT_MASK_DONE 0x20
  43 #define RNGC_CTRL_BIT_AUTO_SEED 0x10
  44
  45 /* the current status for self-test and seed operations */
  46 #define OP_IDLE 0
  47 #define OP_RUN  1
  48 #define OP_DONE 2
  49
  50 static uint64_t imx_rngc_read(void *opaque, hwaddr offset, unsigned size)
  51 {
  52     IMXRNGCState *s = IMX_RNGC(opaque);
  53     uint64_t val = 0;
  54
  55     switch (offset) {
  56     case RNGC_VER_ID:
  57         val |= RNG_TYPE_RNGB << 28 | V_MAJ << 8 | V_MIN;
  58         break;
  59
  60     case RNGC_COMMAND:
  61         if (s->op_seed == OP_RUN) {
  62             val |= RNGC_CMD_BIT_SEED;
  63         }
  64         if (s->op_self_test == OP_RUN) {
  65             val |= RNGC_CMD_BIT_SELF_TEST;
  66         }
  67         break;
  68
  69     case RNGC_CONTROL:
  70         /*
  71          * The CTL_ACC and VERIF_MODE bits are not supported yet.
  72          * They read as 0.
  73          */
  74         val |= s->mask;
  75         if (s->auto_seed) {
  76             val |= RNGC_CTRL_BIT_AUTO_SEED;
  77         }
  78         /*
  79          * We don't have an internal fifo like the real hardware.
  80          * There's no need for strategy to handle fifo underflows.
  81          * We return the FIFO_UFLOW_RESPONSE bits as 0.
  82          */
  83         break;
  84
  85     case RNGC_STATUS:
  86         /*
  87          * We never report any statistics test or self-test errors or any
  88          * other errors. STAT_TEST_PF, ST_PF and ERROR are always 0.
  89          */
  90
  91         /*
  92          * We don't have an internal fifo, see above. Therefore, we
  93          * report back the default fifo size (5 32-bit words) and
  94          * indicate that our fifo is always full.
  95          */
  96         val |= 5 << 12 | 5 << 8;
  97
  98         /* We always have a new seed available. */
  99         val |= 1 << 6;
 100
 101         if (s->op_seed == OP_DONE) {
 102             val |= 1 << 5;
 103         }
 104         if (s->op_self_test == OP_DONE) {
 105             val |= 1 << 4;
 106         }
 107         if (s->op_seed == OP_RUN || s->op_self_test == OP_RUN) {
 108             /*
 109              * We're busy if self-test is running or if we're
 110              * seeding the prng.
 111              */
 112             val |= 1 << 1;
 113         } else {
 114             /*
 115              * We're ready to provide secure random numbers whenever
 116              * we're not busy.
 117              */
 118             val |= 1;
 119         }
 120         break;
 121
 122     case RNGC_FIFO:
 123         qemu_guest_getrandom_nofail(&val, sizeof(val));
 124         break;
 125     }
 126
 127     return val;
 128 }
 129
 130 static void imx_rngc_do_reset(IMXRNGCState *s)
 131 {
 132     s->op_self_test = OP_IDLE;
 133     s->op_seed = OP_IDLE;
 134     s->mask = 0;
 135     s->auto_seed = false;
 136 }
 137
 138 static void imx_rngc_write(void *opaque, hwaddr offset, uint64_t value,
 139                            unsigned size)
 140 {
 141     IMXRNGCState *s = IMX_RNGC(opaque);
 142
 143     switch (offset) {
 144     case RNGC_COMMAND:
 145         if (value & RNGC_CMD_BIT_SW_RST) {
 146             imx_rngc_do_reset(s);
 147         }
 148
 149         /*
 150          * For now, both CLR_ERR and CLR_INT clear the interrupt. We
 151          * don't report any errors yet.
 152          */
 153         if (value & (RNGC_CMD_BIT_CLR_ERR | RNGC_CMD_BIT_CLR_INT)) {
 154             qemu_irq_lower(s->irq);
 155         }
 156
 157         if (value & RNGC_CMD_BIT_SEED) {
 158             s->op_seed = OP_RUN;
 159             qemu_bh_schedule(s->seed_bh);
 160         }
 161
 162         if (value & RNGC_CMD_BIT_SELF_TEST) {
 163             s->op_self_test = OP_RUN;
 164             qemu_bh_schedule(s->self_test_bh);
 165         }
 166         break;
 167
 168     case RNGC_CONTROL:
 169         /*
 170          * The CTL_ACC and VERIF_MODE bits are not supported yet.
 171          * We ignore them if they're set by the caller.
 172          */
 173
 174         if (value & RNGC_CTRL_BIT_MASK_ERR) {
 175             s->mask |= RNGC_CTRL_BIT_MASK_ERR;
 176         } else {
 177             s->mask &= ~RNGC_CTRL_BIT_MASK_ERR;
 178         }
 179
 180         if (value & RNGC_CTRL_BIT_MASK_DONE) {
 181             s->mask |= RNGC_CTRL_BIT_MASK_DONE;
 182         } else {
 183             s->mask &= ~RNGC_CTRL_BIT_MASK_DONE;
 184         }
 185
 186         if (value & RNGC_CTRL_BIT_AUTO_SEED) {
 187             s->auto_seed = true;
 188         } else {
 189             s->auto_seed = false;
 190         }
 191         break;
 192     }
 193 }
 194
 195 static const MemoryRegionOps imx_rngc_ops = {
 196     .read  = imx_rngc_read,
 197     .write = imx_rngc_write,
 198     .endianness = DEVICE_NATIVE_ENDIAN,
 199 };
 200
 201 static void imx_rngc_self_test(void *opaque)
 202 {
 203     IMXRNGCState *s = IMX_RNGC(opaque);
 204
 205     s->op_self_test = OP_DONE;
 206     if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
 207         qemu_irq_raise(s->irq);
 208     }
 209 }
 210
 211 static void imx_rngc_seed(void *opaque)
 212 {
 213     IMXRNGCState *s = IMX_RNGC(opaque);
 214
 215     s->op_seed = OP_DONE;
 216     if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
 217         qemu_irq_raise(s->irq);
 218     }
 219 }
 220
 221 static void imx_rngc_realize(DeviceState *dev, Error **errp)
 222 {
 223     IMXRNGCState *s = IMX_RNGC(dev);
 224     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
 225
 226     memory_region_init_io(&s->iomem, OBJECT(s), &imx_rngc_ops, s,
 227                           TYPE_IMX_RNGC, 0x1000);
 228     sysbus_init_mmio(sbd, &s->iomem);
 229
 230     sysbus_init_irq(sbd, &s->irq);
 231     s->self_test_bh = qemu_bh_new_guarded(imx_rngc_self_test, s,
 232                                           &dev->mem_reentrancy_guard);
 233     s->seed_bh = qemu_bh_new_guarded(imx_rngc_seed, s,
 234                                      &dev->mem_reentrancy_guard);
 235 }
 236
 237 static void imx_rngc_reset(DeviceState *dev)
 238 {
 239     IMXRNGCState *s = IMX_RNGC(dev);
 240
 241     imx_rngc_do_reset(s);
 242 }
 243
 244 static const VMStateDescription vmstate_imx_rngc = {
 245     .name = RNGC_NAME,
 246     .version_id = 1,
 247     .minimum_version_id = 1,
 248     .fields = (const VMStateField[]) {
 249         VMSTATE_UINT8(op_self_test, IMXRNGCState),
 250         VMSTATE_UINT8(op_seed, IMXRNGCState),
 251         VMSTATE_UINT8(mask, IMXRNGCState),
 252         VMSTATE_BOOL(auto_seed, IMXRNGCState),
 253         VMSTATE_END_OF_LIST()
 254     }
 255 };
 256
 257 static void imx_rngc_class_init(ObjectClass *klass, void *data)
 258 {
 259     DeviceClass *dc = DEVICE_CLASS(klass);
 260
 261     dc->realize = imx_rngc_realize;
 262     device_class_set_legacy_reset(dc, imx_rngc_reset);
 263     dc->desc = RNGC_NAME,
 264     dc->vmsd = &vmstate_imx_rngc;
 265 }
 266
 267 static const TypeInfo imx_rngc_info = {
 268     .name          = TYPE_IMX_RNGC,
 269     .parent        = TYPE_SYS_BUS_DEVICE,
 270     .instance_size = sizeof(IMXRNGCState),
 271     .class_init    = imx_rngc_class_init,
 272 };
 273
 274 static void imx_rngc_register_types(void)
 275 {
 276     type_register_static(&imx_rngc_info);
 277 }
 278
 279 type_init(imx_rngc_register_types)