From ae74dc8ae0bff96894d560ec20452bc045b4dd7a Mon Sep 17 00:00:00 2001
From: Nathaniel Wesley Filardo <wes.filardo@scisemi.com>
Date: Mon, 5 May 2025 20:35:59 +0000
Subject: [PATCH] firewall: wait for PHY IRQ before starting stack

Depends on https://github.com/CHERIoT-Platform/cheriot-rtos/pull/530
Work towards https://github.com/lowRISC/sonata-system/issues/410
---
 lib/firewall/firewall.cc | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/firewall/firewall.cc b/lib/firewall/firewall.cc
index a55710e..d3436ee 100644
--- a/lib/firewall/firewall.cc
+++ b/lib/firewall/firewall.cc
@@ -1186,6 +1186,22 @@ bool ethernet_driver_start(std::atomic<uint8_t> *state)
 	auto &ethernet = lazy_network_interface();
 	ethernet.mac_address_set(mac_address());
 	initialize_dns_resolver(firewall_mac_address_get());
+
+	/*
+	 * If the interface link isn't ready, wait for any IRQ.  Acknowledging
+	 * it can't hurt, since the driver's thread's about to go poll for frames.
+	 */
+	{
+		uint32_t firstInterrupt = ethernet.receive_interrupt_value();
+		if (!ethernet.phy_link_status())
+		{
+			Debug::log("Link not ready; wait for first IRQ");
+			Timeout t{UnlimitedTimeout};
+			ethernet.receive_interrupt_complete(&t, firstInterrupt);
+			Debug::log("Link ready? {}", ethernet.phy_link_status());
+		}
+	}
+
 	// Poke the barrier and make the driver thread start.
 	barrier = 2;
 	barrier.notify_one();