[RFC PATCH 3/3] perf: RISC-V: add support for SSE event

[Clément Léger]

In order to use SSE within PMU drivers, register a SSE handler for the
local PMU event. There is not a lot of specific code needed to handle
the SSE event, just reuse the existing overlflow IRQ handler and pass
appropriate pt_regs.

Signed-off-by: Clément Léger <cleger@xxxxxxxxxxxx>
---
 arch/riscv/include/asm/sbi.h |  2 ++
 drivers/perf/riscv_pmu_sbi.c | 51 +++++++++++++++++++++++++++++-------
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 2e99cafe7fed..13b01cd3a814 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -121,6 +121,8 @@ enum sbi_ext_pmu_fid {
 	SBI_EXT_PMU_COUNTER_START,
 	SBI_EXT_PMU_COUNTER_STOP,
 	SBI_EXT_PMU_COUNTER_FW_READ,
+	SBI_EXT_PMU_COUNTER_FW_READ_HI,
+	SBI_EXT_PMU_COUNTER_IRQ_CLEAR,
 };
 
 union sbi_pmu_ctr_info {
diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 96c7f670c8f0..3fca70b13304 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -17,6 +17,7 @@
 #include <linux/irqdomain.h>
 #include <linux/of_irq.h>
 #include <linux/of.h>
+#include <linux/riscv_sse.h>
 #include <linux/cpu_pm.h>
 #include <linux/sched/clock.h>
 
@@ -625,6 +626,12 @@ static inline void pmu_sbi_stop_hw_ctrs(struct riscv_pmu *pmu)
 		  cpu_hw_evt->used_hw_ctrs[0], 0, 0, 0, 0);
 }
 
+static void pmu_sbi_irq_clear(void)
+{
+	/* No need to check the error here as we can't do anything about the error */
+	sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_IRQ_CLEAR, 0, 0, 0, 0, 0, 0);
+}
+
 /*
  * This function starts all the used counters in two step approach.
  * Any counter that did not overflow can be start in a single step
@@ -670,10 +677,10 @@ static inline void pmu_sbi_start_overflow_mask(struct riscv_pmu *pmu,
 	}
 }
 
-static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
+static irqreturn_t pmu_sbi_ovf_handler(struct cpu_hw_events *cpu_hw_evt,
+				       struct pt_regs *regs, bool from_sse)
 {
 	struct perf_sample_data data;
-	struct pt_regs *regs;
 	struct hw_perf_event *hw_evt;
 	union sbi_pmu_ctr_info *info;
 	int lidx, hidx, fidx;
@@ -681,7 +688,6 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 	struct perf_event *event;
 	unsigned long overflow;
 	unsigned long overflowed_ctrs = 0;
-	struct cpu_hw_events *cpu_hw_evt = dev;
 	u64 start_clock = sched_clock();
 
 	if (WARN_ON_ONCE(!cpu_hw_evt))
@@ -691,7 +697,10 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 	fidx = find_first_bit(cpu_hw_evt->used_hw_ctrs, RISCV_MAX_COUNTERS);
 	event = cpu_hw_evt->events[fidx];
 	if (!event) {
-		csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
+		if (from_sse)
+			pmu_sbi_irq_clear();
+		else
+			csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
 		return IRQ_NONE;
 	}
 
@@ -703,16 +712,16 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 
 	/*
 	 * Overflow interrupt pending bit should only be cleared after stopping
-	 * all the counters to avoid any race condition.
+	 * all the counters to avoid any race condition. When using SSE,
+	 * interrupt is cleared when stopping counters.
 	 */
-	csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
+	if (!from_sse)
+		csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
 
 	/* No overflow bit is set */
 	if (!overflow)
 		return IRQ_NONE;
 
-	regs = get_irq_regs();
-
 	for_each_set_bit(lidx, cpu_hw_evt->used_hw_ctrs, RISCV_MAX_COUNTERS) {
 		struct perf_event *event = cpu_hw_evt->events[lidx];
 
@@ -758,6 +767,22 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t pmu_sbi_ovf_irq_handler(int irq, void *dev)
+{
+	return pmu_sbi_ovf_handler(dev, get_irq_regs(), false);
+}
+
+static int pmu_sbi_ovf_sse_handler(uint32_t evt, void *arg,
+				   struct pt_regs *regs)
+{
+	struct cpu_hw_events __percpu *hw_events = arg;
+	struct cpu_hw_events *hw_event = raw_cpu_ptr(hw_events);
+
+	pmu_sbi_ovf_handler(hw_event, regs, true);
+
+	return 0;
+}
+
 static int pmu_sbi_starting_cpu(unsigned int cpu, struct hlist_node *node)
 {
 	struct riscv_pmu *pmu = hlist_entry_safe(node, struct riscv_pmu, node);
@@ -801,9 +826,17 @@ static int pmu_sbi_dying_cpu(unsigned int cpu, struct hlist_node *node)
 static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pdev)
 {
 	int ret;
+	struct sse_event *evt;
 	struct cpu_hw_events __percpu *hw_events = pmu->hw_events;
 	struct irq_domain *domain = NULL;
 
+	evt = sse_event_register(SBI_SSE_EVENT_LOCAL_PMU, 0,
+				 pmu_sbi_ovf_sse_handler, hw_events);
+	if (!IS_ERR(evt)) {
+		sse_event_enable(evt);
+		return 0;
+	}
+
 	if (riscv_isa_extension_available(NULL, SSCOFPMF)) {
 		riscv_pmu_irq_num = RV_IRQ_PMU;
 		riscv_pmu_use_irq = true;
@@ -831,7 +864,7 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pde
 		return -ENODEV;
 	}
 
-	ret = request_percpu_irq(riscv_pmu_irq, pmu_sbi_ovf_handler, "riscv-pmu", hw_events);
+	ret = request_percpu_irq(riscv_pmu_irq, pmu_sbi_ovf_irq_handler, "riscv-pmu", hw_events);
 	if (ret) {
 		pr_err("registering percpu irq failed [%d]\n", ret);
 		return ret;
-- 
2.42.0