[PATCH v3] net: mvneta: re-enable percpu interrupt on resume

[Yun Zhou <yun.zhou@windriver.com>]

On Armada XP (non-armada3700), mvneta uses percpu interrupts where
the ISR (mvneta_percpu_isr) calls disable_percpu_irq() to mask the
MPIC percpu IRQ, then schedules NAPI. NAPI poll completion calls
enable_percpu_irq() to unmask.

If suspend occurs while NAPI is actively polling (between
disable_percpu_irq in the ISR and enable_percpu_irq in
napi_complete_done), the MPIC percpu interrupt remains masked.
mvneta_stop_dev/mvneta_start_dev do not manage the percpu IRQ
enable state -- they only control mvneta's own INTR_NEW_MASK register.

After resume, the MPIC percpu IRQ stays masked permanently: the
network hardware generates interrupts (INTR_NEW_CAUSE != 0) but the
CPU never receives them (irq count stops incrementing), causing a
complete loss of network connectivity.

Fix by calling on_each_cpu(mvneta_percpu_enable) after
mvneta_start_dev() in the resume path, ensuring the MPIC percpu
IRQ is always unmasked regardless of the pre-suspend state.

Fixes: 12bb03b436da ("net: mvneta: Handle per-cpu interrupts")
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
---
v3:
  - Dropped the free_irq/request_irq approach (incorrect root cause).
  - Instead, call on_each_cpu(mvneta_percpu_enable) in the resume path
    to ensure the MPIC percpu IRQ is unmasked, matching mvneta_open().
  - Updated commit message with correct root cause analysis.

v2:
  - Move request_irq before cpuhp registration in resume (matching
    mvneta_open ordering) so that failure does not leave cpuhp
    callbacks registered on a non-functional device.
  - On request_irq failure, call netif_device_detach() to prevent
    further traffic on the dead interface.

 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 b4a845f04c05..5ef79e70e319 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -5907,6 +5907,9 @@ 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
-- 
2.43.0