sifive_prci: Read and write PRCI registers

Writes to the SiFive PRCI registers are preserved while leaving the
ready bits set for the HFX/HFR oscillators and the lock bit set for the
PLL.

Signed-off-by: Nathaniel Graff <nathaniel.graff@sifive.com>
Reviewed-by: Michael Clark <mjc@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

2 files changed, 73 insertions, 8 deletions

diff --git a/hw/riscv/sifive_prci.c b/hw/riscv/sifive_prci.c
index fa136b5..f406682 100644
--- a/hw/riscv/sifive_prci.c
+++ b/hw/riscv/sifive_prci.c
@@ -24,15 +24,18 @@
 #include "target/riscv/cpu.h"
 #include "hw/riscv/sifive_prci.h"
 
-/* currently implements enough to mock freedom-e-sdk BSP clock programming */
-
 static uint64_t sifive_prci_read(void *opaque, hwaddr addr, unsigned int size)
 {
-    if (addr == 0 /* PRCI_HFROSCCFG */) {
-        return 1 << 31; /* ROSC_RDY */
-    }
-    if (addr == 8 /* PRCI_PLLCFG    */) {
-        return 1 << 31; /* PLL_LOCK */
+    SiFivePRCIState *s = opaque;
+    switch (addr) {
+    case SIFIVE_PRCI_HFROSCCFG:
+        return s->hfrosccfg;
+    case SIFIVE_PRCI_HFXOSCCFG:
+        return s->hfxosccfg;
+    case SIFIVE_PRCI_PLLCFG:
+        return s->pllcfg;
+    case SIFIVE_PRCI_PLLOUTDIV:
+        return s->plloutdiv;
     }
     hw_error("%s: read: addr=0x%x\n", __func__, (int)addr);
     return 0;
@@ -41,7 +44,30 @@ static uint64_t sifive_prci_read(void *opaque, hwaddr addr, unsigned int size)
 static void sifive_prci_write(void *opaque, hwaddr addr,
            uint64_t val64, unsigned int size)
 {
-    /* discard writes */
+    SiFivePRCIState *s = opaque;
+    switch (addr) {
+    case SIFIVE_PRCI_HFROSCCFG:
+        s->hfrosccfg = (uint32_t) val64;
+        /* OSC stays ready */
+        s->hfrosccfg |= SIFIVE_PRCI_HFROSCCFG_RDY;
+        break;
+    case SIFIVE_PRCI_HFXOSCCFG:
+        s->hfxosccfg = (uint32_t) val64;
+        /* OSC stays ready */
+        s->hfxosccfg |= SIFIVE_PRCI_HFXOSCCFG_RDY;
+        break;
+    case SIFIVE_PRCI_PLLCFG:
+        s->pllcfg = (uint32_t) val64;
+        /* PLL stays locked */
+        s->pllcfg |= SIFIVE_PRCI_PLLCFG_LOCK;
+        break;
+    case SIFIVE_PRCI_PLLOUTDIV:
+        s->plloutdiv = (uint32_t) val64;
+        break;
+    default:
+        hw_error("%s: bad write: addr=0x%x v=0x%x\n",
+                 __func__, (int)addr, (int)val64);
+    }
 }
 
 static const MemoryRegionOps sifive_prci_ops = {
@@ -61,6 +87,13 @@ static void sifive_prci_init(Object *obj)
     memory_region_init_io(&s->mmio, obj, &sifive_prci_ops, s,
                           TYPE_SIFIVE_PRCI, 0x8000);
     sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
+
+    s->hfrosccfg = (SIFIVE_PRCI_HFROSCCFG_RDY | SIFIVE_PRCI_HFROSCCFG_EN);
+    s->hfxosccfg = (SIFIVE_PRCI_HFROSCCFG_RDY | SIFIVE_PRCI_HFROSCCFG_EN);
+    s->pllcfg = (SIFIVE_PRCI_PLLCFG_REFSEL | SIFIVE_PRCI_PLLCFG_BYPASS |
+                SIFIVE_PRCI_PLLCFG_LOCK);
+    s->plloutdiv = SIFIVE_PRCI_PLLOUTDIV_DIV1;
+
 }
 
 static const TypeInfo sifive_prci_info = {
diff --git a/include/hw/riscv/sifive_prci.h b/include/hw/riscv/sifive_prci.h
index b6f4c48..bd51c4a 100644
--- a/include/hw/riscv/sifive_prci.h
+++ b/include/hw/riscv/sifive_prci.h
@@ -19,6 +19,34 @@
 #ifndef HW_SIFIVE_PRCI_H
 #define HW_SIFIVE_PRCI_H
 
+enum {
+    SIFIVE_PRCI_HFROSCCFG   = 0x0,
+    SIFIVE_PRCI_HFXOSCCFG   = 0x4,
+    SIFIVE_PRCI_PLLCFG      = 0x8,
+    SIFIVE_PRCI_PLLOUTDIV   = 0xC
+};
+
+enum {
+    SIFIVE_PRCI_HFROSCCFG_RDY   = (1 << 31),
+    SIFIVE_PRCI_HFROSCCFG_EN    = (1 << 30)
+};
+
+enum {
+    SIFIVE_PRCI_HFXOSCCFG_RDY   = (1 << 31),
+    SIFIVE_PRCI_HFXOSCCFG_EN    = (1 << 30)
+};
+
+enum {
+    SIFIVE_PRCI_PLLCFG_PLLSEL   = (1 << 16),
+    SIFIVE_PRCI_PLLCFG_REFSEL   = (1 << 17),
+    SIFIVE_PRCI_PLLCFG_BYPASS   = (1 << 18),
+    SIFIVE_PRCI_PLLCFG_LOCK     = (1 << 31)
+};
+
+enum {
+    SIFIVE_PRCI_PLLOUTDIV_DIV1  = (1 << 8)
+};
+
 #define TYPE_SIFIVE_PRCI "riscv.sifive.prci"
 
 #define SIFIVE_PRCI(obj) \
@@ -30,6 +58,10 @@ typedef struct SiFivePRCIState {
 
     /*< public >*/
     MemoryRegion mmio;
+    uint32_t hfrosccfg;
+    uint32_t hfxosccfg;
+    uint32_t pllcfg;
+    uint32_t plloutdiv;
 } SiFivePRCIState;
 
 DeviceState *sifive_prci_create(hwaddr addr);