[PATCH 7.0.y 1/5] net: mvneta: re-enable percpu interrupt on resume

[Arbab Haider <arbabhaider649@gmail.com>]

From: Yun Zhou <yun.zhou@windriver.com>

On Marvell MPIC platforms (Armada 370/XP/38x), mvneta uses a percpu
IRQ disable/enable scheme for NAPI: the ISR (mvneta_percpu_isr) calls
disable_percpu_irq() to mask the MPIC per-CPU interrupt and schedules
NAPI poll, which calls enable_percpu_irq() on completion to unmask.

If suspend occurs while NAPI poll is pending (between
disable_percpu_irq in the ISR and enable_percpu_irq in poll
completion), the interrupt is never re-enabled:

  1. mvneta_percpu_isr: disable_percpu_irq() + napi_schedule()
     => MPIC masked, percpu_enabled cpumask bit cleared
  2. NAPI poll does not complete before suspend proceeds
     (on PREEMPT_RT this is highly likely since softirqs run in
     ksoftirqd which gets frozen; on non-RT it can happen when
     softirq processing is deferred to ksoftirqd)
  3. mvneta_stop_dev => napi_disable(): cancels the pending poll
     without executing the completion path
  4. suspend_device_irqs => IRQCHIP_MASK_ON_SUSPEND: masks MPIC
     (already masked, but records IRQS_SUSPENDED)
  5. Resume: mpic_resume checks irq_percpu_is_enabled() => false
     (bit was cleared in step 1) => skips unmask
  6. mvneta_start_dev only restores device-level INTR_NEW_MASK,
     does not touch the MPIC per-CPU mask

Result: MPIC per-CPU interrupt stays masked permanently. The NIC
generates interrupts (INTR_NEW_CAUSE != 0) but the CPU never
receives them, causing complete loss of network connectivity.

Fix by calling on_each_cpu(mvneta_percpu_enable) in the resume path
to unconditionally unmask the MPIC per-CPU interrupt regardless of
pre-suspend state.

Fixes: 12bb03b436da ("net: mvneta: Handle per-cpu interrupts")
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260622074350.1666290-1-yun.zhou@windriver.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Upstream commit fd398d6480987e4c84fff0aaab6b9d6642a93343 ]

---
 drivers/net/ethernet/marvell/mvneta.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 9ba4aef7080c..22da95d46bef 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -5897,6 +5897,9 @@ static int mvneta_resume(struct device *device)
 	rtnl_unlock();
 	mvneta_set_rx_mode(dev);
 
+	if (!pp->neta_armada3700)
+		on_each_cpu(mvneta_percpu_enable, pp, true);
+
 	return 0;
 }
 #endif
-- 
2.53.0