net: lantiq: disable interrupt before sheduling NAPI

[ Upstream commit f2386cf ]

This patch fixes TX hangs with threaded NAPI enabled. The scheduled
NAPI seems to be executed in parallel with the interrupt on second
thread. Sometimes it happens that ltq_dma_disable_irq() is executed
after xrx200_tx_housekeeping(). The symptom is that TX interrupts
are disabled in the DMA controller. As a result, the TX hangs after
a few seconds of the iperf test. Scheduling NAPI after disabling
interrupts fixes this issue.

Tested on Lantiq xRX200 (BT Home Hub 5A).

Fixes: 9423361 ("net: lantiq: Disable IRQs only if NAPI gets scheduled ")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/lantiq_xrx200.c

@@ -352,8 +352,8 @@ static irqreturn_t xrx200_dma_irq(int irq, void *ptr)
 	struct xrx200_chan *ch = ptr;
 
 	if (napi_schedule_prep(&ch->napi)) {
-		__napi_schedule(&ch->napi);
 		ltq_dma_disable_irq(&ch->dma);
+		__napi_schedule(&ch->napi);
 	}
 
 	ltq_dma_ack_irq(&ch->dma);