lib: sbi_pmu: Fix counter and event info error codes as per SBI v3.0 spec

Align the PMU extension implementation with the error codes required
by the SBI v3.0 specification, chapter 11:

 - sbi_pmu_counter_start and sbi_pmu_counter_stop (secs 11.9-11.10,
   tables 39-42): the start_flags/stop_flags bits 2:(XLEN-1) are
   reserved and must be zero, so return SBI_ERR_INVALID_PARAM when any
   reserved flag bit is set. Introduce SBI_PMU_START_FLAGS_MASK and
   SBI_PMU_STOP_FLAGS_MASK for the valid bits of each function.

 - sbi_pmu_counter_start and sbi_pmu_counter_stop (tables 40 and 42):
   return SBI_ERR_ALREADY_STARTED / SBI_ERR_ALREADY_STOPPED when the
   set of counters includes a counter which is already started or
   stopped, instead of ignoring the error returned for each counter.

 - sbi_pmu_event_get_info (sec 11.14, table 47): the output word must
   indicate whether the event is supported, but firmware events were
   only matched against the hardware event map and were always
   reported as unsupported. Report a validated firmware event as
   supported.

Signed-off-by: David E. Garcia Porras <david.garcia@aheadcomputing.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260818210023.466462-4-david.garcia@aheadcomputing.com
Signed-off-by: Anup Patel <anup@brainfault.org>

include/sbi/sbi_ecall_interface.h

@@ -306,10 +306,22 @@ struct sbi_pmu_event_info {
 /* Flags defined for counter start function */
 #define SBI_PMU_START_FLAG_SET_INIT_VALUE (1 << 0)
 #define SBI_PMU_START_FLAG_INIT_FROM_SNAPSHOT (1 << 1)
+/* Start flags valid mask */
+#define SBI_PMU_START_FLAGS_MASK	\
+	( \
+		SBI_PMU_START_FLAG_SET_INIT_VALUE | \
+		SBI_PMU_START_FLAG_INIT_FROM_SNAPSHOT \
+	)
 
 /* Flags defined for counter stop function */
 #define SBI_PMU_STOP_FLAG_RESET (1 << 0)
 #define SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT (1 << 1)
+/* Stop flags valid mask */
+#define SBI_PMU_STOP_FLAGS_MASK	\
+	( \
+		SBI_PMU_STOP_FLAG_RESET | \
+		SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT \
+	)
 
 /* SBI function IDs for DBCN extension */
 #define SBI_EXT_DBCN_CONSOLE_WRITE		0x0

lib/sbi/sbi_pmu.c

@@ -574,6 +574,9 @@ int sbi_pmu_ctr_start(unsigned long cbase, unsigned long cmask,
 	if (!pmu_ctr_idx_validate(cbase, cmask))
 		return ret;
 
+	if (flags & ~SBI_PMU_START_FLAGS_MASK)
+		return SBI_ERR_INVALID_PARAM;
+
 	if (flags & SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT)
 		return SBI_ENO_SHMEM;
 
@@ -592,6 +595,8 @@ int sbi_pmu_ctr_start(unsigned long cbase, unsigned long cmask,
 				 : 0x0;
 			ret = pmu_ctr_start_fw(phs, cidx, event_code, edata,
 					       ival, bUpdate);
+			if (ret)
+				return ret;
 		} else {
 			if (cidx >= 3) {
 				struct sbi_pmu_hw_event_config *ev_cfg =
@@ -605,6 +610,8 @@ int sbi_pmu_ctr_start(unsigned long cbase, unsigned long cmask,
 					return ret;
 			}
 			ret = pmu_ctr_start_hw(cidx, ival, bUpdate);
+			if (ret)
+				return ret;
 		}
 	}
 
@@ -693,6 +700,9 @@ int sbi_pmu_ctr_stop(unsigned long cbase, unsigned long cmask,
 	if (!pmu_ctr_idx_validate(cbase, cmask))
 		return ret;
 
+	if (flag & ~SBI_PMU_STOP_FLAGS_MASK)
+		return SBI_ERR_INVALID_PARAM;
+
 	if (flag & SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT)
 		return SBI_ENO_SHMEM;
 
@@ -708,6 +718,9 @@ int sbi_pmu_ctr_stop(unsigned long cbase, unsigned long cmask,
 		else
 			ret = pmu_ctr_stop_hw(cidx);
 
+		if(ret)
+			return ret;
+
 		if (cidx > (CSR_INSTRET - CSR_CYCLE) && flag & SBI_PMU_STOP_FLAG_RESET) {
 			phs->active_events[cidx] = SBI_PMU_EVENT_IDX_INVALID;
 			pmu_reset_hw_mhpmevent(cidx);
@@ -1104,6 +1117,8 @@ int sbi_pmu_event_get_info(unsigned long shmem_phys_lo, unsigned long shmem_phys
 		event_type = pmu_event_validate(phs, event_idx, einfo[i].event_data);
 		if (event_type < 0) {
 			einfo[i].output = 0;
+		} else if (event_type == SBI_PMU_EVENT_TYPE_FW) {
+			einfo[i].output = 1;
 		} else {
 			for (j = 0; j < num_hw_events; j++) {
 				temp = &hw_event_map[j];