[PATCH 4/7] riscv: Clear pending IPIs on initialization

[Sean Anderson]

Even though we no longer call smp_function if an IPI was not sent by
U-Boot, we still need to clear any IPIs which were pending from the
execution environment. Otherwise, secondary harts will busy-wait in
secondary_hart_loop, instead of relaxing.

Signed-off-by: Sean Anderson <seanga2 at gmail.com>
---

 arch/riscv/cpu/cpu.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
index bfa2d4a426..ad94744c0f 100644
--- a/arch/riscv/cpu/cpu.c
+++ b/arch/riscv/cpu/cpu.c
@@ -72,6 +72,15 @@ static int riscv_cpu_probe(void)
 	return 0;
 }
 
+/*
+ * This is called on secondary harts just after the IPI is init'd. Currently
+ * there's nothing to do, since we just need to clear any existing IPIs, and
+ * that is handled by the sending of an ipi itself.
+ */
+void riscv_ipi_init_secondary_hart(ulong hart, ulong arg0, ulong arg1)
+{
+}
+
 int arch_cpu_init_dm(void)
 {
 	int ret;
@@ -111,6 +120,15 @@ int arch_cpu_init_dm(void)
 	ret = riscv_init_ipi();
 	if (ret)
 		return ret;
+
+	/*
+	 * Clear all pending IPIs on secondary harts. We don't do anything on
+	 * the boot hart, since we never send an IPI to ourselves, and no
+	 * interrupts are enabled
+	 */
+	ret = smp_call_function((ulong)riscv_ipi_init_secondary_hart, 0, 0, 0);
+	if (ret)
+		return ret;
 #endif
 
 	return 0;
-- 
2.28.0