hw/riscv/riscv-iommu: add IOCOUNTINH mmio writes

RISCV_IOMMU_REG_IOCOUNTINH is done by riscv_iommu_process_iocntinh_cy(),
which is called during riscv_iommu_mmio_write() callback via a new
riscv_iommu_pricess_hpm_writes() helper.

Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250224190826.1858473-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/hw/riscv/riscv-iommu-hpm.c b/hw/riscv/riscv-iommu-hpm.c
index 325088333e..70814b942d 100644
--- a/hw/riscv/riscv-iommu-hpm.c
+++ b/hw/riscv/riscv-iommu-hpm.c
@@ -202,3 +202,63 @@ void riscv_iommu_hpm_timer_cb(void *priv)
         riscv_iommu_notify(s, RISCV_IOMMU_INTR_PM);
     }
 }
+
+static void hpm_setup_timer(RISCVIOMMUState *s, uint64_t value)
+{
+    const uint32_t inhibit = riscv_iommu_reg_get32(
+        s, RISCV_IOMMU_REG_IOCOUNTINH);
+    uint64_t overflow_at, overflow_ns;
+
+    if (get_field(inhibit, RISCV_IOMMU_IOCOUNTINH_CY)) {
+        return;
+    }
+
+    /*
+     * We are using INT64_MAX here instead to UINT64_MAX because cycle counter
+     * has 63-bit precision and INT64_MAX is the maximum it can store.
+     */
+    if (value) {
+        overflow_ns = INT64_MAX - value + 1;
+    } else {
+        overflow_ns = INT64_MAX;
+    }
+
+    overflow_at = (uint64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + overflow_ns;
+
+    if (overflow_at > INT64_MAX) {
+        s->irq_overflow_left = overflow_at - INT64_MAX;
+        overflow_at = INT64_MAX;
+    }
+
+    timer_mod_anticipate_ns(s->hpm_timer, overflow_at);
+}
+
+/* Updates the internal cycle counter state when iocntinh:CY is changed. */
+void riscv_iommu_process_iocntinh_cy(RISCVIOMMUState *s, bool prev_cy_inh)
+{
+    const uint32_t inhibit = riscv_iommu_reg_get32(
+        s, RISCV_IOMMU_REG_IOCOUNTINH);
+
+    /* We only need to process CY bit toggle. */
+    if (!(inhibit ^ prev_cy_inh)) {
+        return;
+    }
+
+    if (!(inhibit & RISCV_IOMMU_IOCOUNTINH_CY)) {
+        /*
+         * Cycle counter is enabled. Just start the timer again and update
+         * the clock snapshot value to point to the current time to make
+         * sure iohpmcycles read is correct.
+         */
+        s->hpmcycle_prev = get_cycles();
+        hpm_setup_timer(s, s->hpmcycle_val);
+    } else {
+        /*
+         * Cycle counter is disabled. Stop the timer and update the cycle
+         * counter to record the current value which is last programmed
+         * value + the cycles passed so far.
+         */
+        s->hpmcycle_val = s->hpmcycle_val + (get_cycles() - s->hpmcycle_prev);
+        timer_del(s->hpm_timer);
+    }
+}