[v1 03/10] drivers/perf: riscv: Read upper bits of a firmware counter

[Atish Patra]

SBI v2.0 introduced a explicit function to read the upper 32 bits
for any firmwar counter width that is longer than 32bits.
This is only applicable for RV32 where firmware counter can be
64 bit.

Signed-off-by: Atish Patra <atishp at rivosinc.com>
---
 drivers/perf/riscv_pmu_sbi.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 16acd4dcdb96..646604f8c0a5 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -35,6 +35,8 @@
 PMU_FORMAT_ATTR(event, "config:0-47");
 PMU_FORMAT_ATTR(firmware, "config:63");
 
+static bool sbi_v2_available;
+
 static struct attribute *riscv_arch_formats_attr[] = {
 	&format_attr_event.attr,
 	&format_attr_firmware.attr,
@@ -488,16 +490,23 @@ static u64 pmu_sbi_ctr_read(struct perf_event *event)
 	struct hw_perf_event *hwc = &event->hw;
 	int idx = hwc->idx;
 	struct sbiret ret;
-	union sbi_pmu_ctr_info info;
 	u64 val = 0;
+	union sbi_pmu_ctr_info info = pmu_ctr_list[idx];
 
 	if (pmu_sbi_is_fw_event(event)) {
 		ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_FW_READ,
 				hwc->idx, 0, 0, 0, 0, 0);
-		if (!ret.error)
-			val = ret.value;
+		if (ret.error)
+			return val;
+
+		val = ret.value;
+		if (IS_ENABLED(CONFIG_32BIT) && sbi_v2_available && info.width >= 32) {
+			ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_FW_READ_HI,
+					hwc->idx, 0, 0, 0, 0, 0);
+			if (!ret.error)
+				val |= ((u64)ret.value << 32);
+		}
 	} else {
-		info = pmu_ctr_list[idx];
 		val = riscv_pmu_ctr_read_csr(info.csr);
 		if (IS_ENABLED(CONFIG_32BIT))
 			val = ((u64)riscv_pmu_ctr_read_csr(info.csr + 0x80)) << 31 | val;
@@ -1108,6 +1117,9 @@ static int __init pmu_sbi_devinit(void)
 		return 0;
 	}
 
+	if (sbi_spec_version >= sbi_mk_version(2, 0))
+		sbi_v2_available = true;
+
 	ret = cpuhp_setup_state_multi(CPUHP_AP_PERF_RISCV_STARTING,
 				      "perf/riscv/pmu:starting",
 				      pmu_sbi_starting_cpu, pmu_sbi_dying_cpu);
-- 
2.34.1