drivers/perf: riscv: Read upper bits of a firmware counter

SBI v2.0 introduced a explicit function to read the upper 32 bits
for any firmware counter width that is longer than 32bits.
This is only applicable for RV32 where firmware counter can be
64 bit.
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240420151741.962500-4-atishp@rivosinc.comSigned-off-by: Anup Patel <anup@brainfault.org>

drivers/perf/riscv_pmu_sbi.c

@@ -57,6 +57,8 @@ asm volatile(ALTERNATIVE(						\
 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,
@@ -511,19 +513,29 @@ 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 0;
+
+		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
+				WARN_ONCE(1, "Unable to read upper 32 bits of firmware counter error: %ld\n",
+					  ret.error);
+		}
 	} 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;
+			val |= ((u64)riscv_pmu_ctr_read_csr(info.csr + 0x80)) << 32;
 	}
 
 	return val;
@@ -1135,6 +1147,9 @@ 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);