1 files changed, 151 insertions, 0 deletions
diff --git a/triscv/src/mmu.c b/triscv/src/mmu.c
new file mode 100644
index 0000000..c73f91d
--- /dev/null
+++ b/triscv/src/mmu.c
@@ -0,0 +1,151 @@
+#include <triscv/mmu.h>
+
+struct tlb_map {
+	vm_t from;
+	pm_t to;
+	bool valid;
+};
+
+struct dev_map {
+	pm_t start;
+	struct dev dev;
+};
+
+/* completely arbitrary value */
+#define MMU_SIZE 1024
+#define MAX_DEVS 16
+struct mmu {
+	/* virtual -> physical */
+	struct tlb_map tlb[MMU_SIZE];
+
+	/* physical to dev */
+	struct dev_map dev[MAX_DEVS];
+	size_t devs;
+
+	/* whether we should treat incoming addresses as virtual or physical */
+	bool translate;
+};
+
+struct mmu *mmu_create()
+{
+	/** @todo map some backing memory as well */
+	return calloc(1, sizeof(struct mmu));
+}
+
+void mmu_destroy(struct mmu *mmu)
+{
+	free(mmu);
+}
+
+static struct dev_map *mmu_find_dev_map(struct mmu *mmu, pm_t addr)
+{
+	for (size_t i = 0; i < mmu->devs; ++i) {
+		struct dev_map *d = &mmu->dev[i];
+		if (d->start > addr)
+			continue;
+
+		/* slightly tricky off by one here */
+		if (d->dev.size <= (addr - d->start))
+			continue;
+
+		return d;
+	}
+
+	return NULL;
+}
+
+stat_t mmu_map_dev(struct mmu *mmu, pm_t start, struct dev dev)
+{
+	/** @todo return status or something */
+	if (mmu->devs == MAX_DEVS)
+		return ERR_FULL;
+
+	if (mmu_find_dev_map(mmu, start))
+		return ERR_EXISTS;
+
+	struct dev_map *d = &mmu->dev[mmu->devs++];
+	d->dev = dev;
+	d->start = start;
+	return OK;
+}
+
+void mmu_enable(struct mmu *mmu)
+{
+	mmu->translate = true;
+}
+
+void mmu_disable(struct mmu *mmu)
+{
+	mmu->translate = false;
+}
+
+static bool mmu_translate(struct cpu *cpu, struct mmu *mmu, vm_t *addr)
+{
+	(void)cpu;
+	(void)mmu;
+	(void)addr;
+	/** @todo raise segfault if addr is not allowed */
+	return true;
+}
+
+void mmu_write1(struct cpu *cpu, struct mmu *mmu, vm_t addr, tri_t t)
+{
+	if (mmu->translate) {
+		if (!mmu_translate(cpu, mmu, &addr))
+			return;
+	}
+
+	struct dev_map *d = mmu_find_dev_map(mmu, addr);
+	if (!d || !d->dev.write1) {
+		/** @todo raise bus (?) error */
+	}
+
+	d->dev.write1(cpu, d->dev.dev, addr - d->start, t);
+}
+
+void mmu_write3(struct cpu *cpu, struct mmu *mmu, vm_t addr, tri_t t)
+{
+	if (mmu->translate) {
+		if (!mmu_translate(cpu, mmu, &addr))
+			return;
+	}
+
+	struct dev_map *d = mmu_find_dev_map(mmu, addr);
+	if (!d || !d->dev.write3) {
+		/** @todo raise bus error */
+	}
+
+	d->dev.write3(cpu, d->dev.dev, addr - d->start, t);
+}
+
+tri_t mmu_read1(struct cpu *cpu, struct mmu *mmu, vm_t addr)
+{
+	if (mmu->translate) {
+		if (!mmu_translate(cpu, mmu, &addr))
+			return 0;
+	}
+
+	struct dev_map *d = mmu_find_dev_map(mmu, addr);
+	if (!d || !d->dev.read1) {
+		/** @todo raise bus error */
+		return 0;
+	}
+
+	return d->dev.read1(cpu, d->dev.dev, addr - d->start);
+}
+
+tri_t mmu_read3(struct cpu *cpu, struct mmu *mmu, vm_t addr)
+{
+	if (mmu->translate) {
+		if (!mmu_translate(cpu, mmu, &addr))
+			return 0;
+	}
+
+	struct dev_map *d = mmu_find_dev_map(mmu, addr);
+	if (!d || !d->dev.read3) {
+		/** @todo raise bus error */
+		return 0;
+	}
+
+	return d->dev.read3(cpu, d->dev.dev, addr - d->start);
+}