sbi: sbi_pmu: Improve sbi_pmu_init() error handling

This patch makes the following changes:

- As sbi_platform_pmu_init() returns a negative error code on
  failure, let sbi_pmu_init() print out the error code with
  sbi_dprintf().

- In order to distinguish the SBI_EFAIL error returned by
  sbi_pmu_add_*_counter_map(), return SBI_ENOENT to indicate
  that fdt_pmu_setup() failed to locate "riscv,pmu" node, and
  generic_pmu_init() ignores such case.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>

lib/sbi/sbi_pmu.c

@@ -957,6 +957,7 @@ int sbi_pmu_init(struct sbi_scratch *scratch, bool cold_boot)
 	int hpm_count = sbi_fls(sbi_hart_mhpm_mask(scratch));
 	struct sbi_pmu_hart_state *phs;
 	const struct sbi_platform *plat;
+	int rc;
 
 	if (cold_boot) {
 		hw_event_map = sbi_calloc(sizeof(*hw_event_map),
@@ -972,7 +973,10 @@ int sbi_pmu_init(struct sbi_scratch *scratch, bool cold_boot)
 
 		plat = sbi_platform_ptr(scratch);
 		/* Initialize hw pmu events */
-		sbi_platform_pmu_init(plat);
+		rc = sbi_platform_pmu_init(plat);
+		if (rc)
+			sbi_dprintf("%s: platform pmu init failed "
+				    "(error %d)\n", __func__, rc);
 
 		/* mcycle & minstret is available always */
 		if (!hpm_count)

lib/utils/fdt/fdt_pmu.c

@@ -74,7 +74,7 @@ int fdt_pmu_setup(void *fdt)
 
 	pmu_offset = fdt_node_offset_by_compatible(fdt, -1, "riscv,pmu");
 	if (pmu_offset < 0)
-		return SBI_EFAIL;
+		return SBI_ENOENT;
 
 	event_ctr_map = fdt_getprop(fdt, pmu_offset,
 				    "riscv,event-to-mhpmcounters", &len);

platform/generic/platform.c

@@ -265,7 +265,13 @@ static u32 generic_tlb_num_entries(void)
 
 static int generic_pmu_init(void)
 {
-	return fdt_pmu_setup(fdt_get_address());
+	int rc;
+
+	rc = fdt_pmu_setup(fdt_get_address());
+	if (rc && rc != SBI_ENOENT)
+		return rc;
+
+	return 0;
 }
 
 static uint64_t generic_pmu_xlate_to_mhpmevent(uint32_t event_idx,