hw/riscv: virt: Add PMU DT node to the device tree

Qemu virt machine can support few cache events and cycle/instret counters.
It also supports counter overflow for these events.

Add a DT node so that OpenSBI/Linux kernel is aware of the virt machine
capabilities. There are some dummy nodes added for testing as well.

Acked-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Message-Id: <20220824221701.41932-5-atishp@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

3 files changed, 74 insertions, 0 deletions

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index ff8c0df..befa9d2 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -30,6 +30,7 @@
 #include "hw/char/serial.h"
 #include "target/riscv/cpu.h"
 #include "hw/core/sysbus-fdt.h"
+#include "target/riscv/pmu.h"
 #include "hw/riscv/riscv_hart.h"
 #include "hw/riscv/virt.h"
 #include "hw/riscv/boot.h"
@@ -708,6 +709,20 @@ static void create_fdt_socket_aplic(RISCVVirtState *s,
     aplic_phandles[socket] = aplic_s_phandle;
 }
 
+static void create_fdt_pmu(RISCVVirtState *s)
+{
+    char *pmu_name;
+    MachineState *mc = MACHINE(s);
+    RISCVCPU hart = s->soc[0].harts[0];
+
+    pmu_name = g_strdup_printf("/soc/pmu");
+    qemu_fdt_add_subnode(mc->fdt, pmu_name);
+    qemu_fdt_setprop_string(mc->fdt, pmu_name, "compatible", "riscv,pmu");
+    riscv_pmu_generate_fdt_node(mc->fdt, hart.cfg.pmu_num, pmu_name);
+
+    g_free(pmu_name);
+}
+
 static void create_fdt_sockets(RISCVVirtState *s, const MemMapEntry *memmap,
                                bool is_32_bit, uint32_t *phandle,
                                uint32_t *irq_mmio_phandle,
@@ -1036,6 +1051,7 @@ static void create_fdt(RISCVVirtState *s, const MemMapEntry *memmap,
 
     create_fdt_flash(s, memmap);
     create_fdt_fw_cfg(s, memmap);
+    create_fdt_pmu(s);
 
 update_bootargs:
     if (cmdline && *cmdline) {
diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
index a5f504e..b8e56d2 100644
--- a/target/riscv/pmu.c
+++ b/target/riscv/pmu.c
@@ -20,11 +20,68 @@
 #include "cpu.h"
 #include "pmu.h"
 #include "sysemu/cpu-timers.h"
+#include "sysemu/device_tree.h"
 
 #define RISCV_TIMEBASE_FREQ 1000000000 /* 1Ghz */
 #define MAKE_32BIT_MASK(shift, length) \
         (((uint32_t)(~0UL) >> (32 - (length))) << (shift))
 
+/*
+ * To keep it simple, any event can be mapped to any programmable counters in
+ * QEMU. The generic cycle & instruction count events can also be monitored
+ * using programmable counters. In that case, mcycle & minstret must continue
+ * to provide the correct value as well. Heterogeneous PMU per hart is not
+ * supported yet. Thus, number of counters are same across all harts.
+ */
+void riscv_pmu_generate_fdt_node(void *fdt, int num_ctrs, char *pmu_name)
+{
+    uint32_t fdt_event_ctr_map[20] = {};
+    uint32_t cmask;
+
+    /* All the programmable counters can map to any event */
+    cmask = MAKE_32BIT_MASK(3, num_ctrs);
+
+   /*
+    * The event encoding is specified in the SBI specification
+    * Event idx is a 20bits wide number encoded as follows:
+    * event_idx[19:16] = type
+    * event_idx[15:0] = code
+    * The code field in cache events are encoded as follows:
+    * event_idx.code[15:3] = cache_id
+    * event_idx.code[2:1] = op_id
+    * event_idx.code[0:0] = result_id
+    */
+
+   /* SBI_PMU_HW_CPU_CYCLES: 0x01 : type(0x00) */
+   fdt_event_ctr_map[0] = cpu_to_be32(0x00000001);
+   fdt_event_ctr_map[1] = cpu_to_be32(0x00000001);
+   fdt_event_ctr_map[2] = cpu_to_be32(cmask | 1 << 0);
+
+   /* SBI_PMU_HW_INSTRUCTIONS: 0x02 : type(0x00) */
+   fdt_event_ctr_map[3] = cpu_to_be32(0x00000002);
+   fdt_event_ctr_map[4] = cpu_to_be32(0x00000002);
+   fdt_event_ctr_map[5] = cpu_to_be32(cmask | 1 << 2);
+
+   /* SBI_PMU_HW_CACHE_DTLB : 0x03 READ : 0x00 MISS : 0x00 type(0x01) */
+   fdt_event_ctr_map[6] = cpu_to_be32(0x00010019);
+   fdt_event_ctr_map[7] = cpu_to_be32(0x00010019);
+   fdt_event_ctr_map[8] = cpu_to_be32(cmask);
+
+   /* SBI_PMU_HW_CACHE_DTLB : 0x03 WRITE : 0x01 MISS : 0x00 type(0x01) */
+   fdt_event_ctr_map[9] = cpu_to_be32(0x0001001B);
+   fdt_event_ctr_map[10] = cpu_to_be32(0x0001001B);
+   fdt_event_ctr_map[11] = cpu_to_be32(cmask);
+
+   /* SBI_PMU_HW_CACHE_ITLB : 0x04 READ : 0x00 MISS : 0x00 type(0x01) */
+   fdt_event_ctr_map[12] = cpu_to_be32(0x00010021);
+   fdt_event_ctr_map[13] = cpu_to_be32(0x00010021);
+   fdt_event_ctr_map[14] = cpu_to_be32(cmask);
+
+   /* This a OpenSBI specific DT property documented in OpenSBI docs */
+   qemu_fdt_setprop(fdt, pmu_name, "riscv,event-to-mhpmcounters",
+                    fdt_event_ctr_map, sizeof(fdt_event_ctr_map));
+}
+
 static bool riscv_pmu_counter_valid(RISCVCPU *cpu, uint32_t ctr_idx)
 {
     if (ctr_idx < 3 || ctr_idx >= RV_MAX_MHPMCOUNTERS ||
diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
index 0366536..3004ce3 100644
--- a/target/riscv/pmu.h
+++ b/target/riscv/pmu.h
@@ -31,5 +31,6 @@ int riscv_pmu_init(RISCVCPU *cpu, int num_counters);
 int riscv_pmu_update_event_map(CPURISCVState *env, uint64_t value,
                                uint32_t ctr_idx);
 int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx);
+void riscv_pmu_generate_fdt_node(void *fdt, int num_counters, char *pmu_name);
 int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value,
                           uint32_t ctr_idx);