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From:   Aleksander Jan Bajkowski <olek2@wp.pl>
To:     hauke@hauke-m.de, davem@davemloft.net, kuba@kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Aleksander Jan Bajkowski <olek2@wp.pl>
Subject: [PATCH net] net: lantiq: disable interrupt before sheduling NAPI
Date:   Tue,  8 Jun 2021 23:21:07 +0200
Message-Id: <20210608212107.222690-1-olek2@wp.pl>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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: 9423361da523 ("net: lantiq: Disable IRQs only if NAPI gets scheduled ")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
---
 drivers/net/ethernet/lantiq_xrx200.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 36dc3e5f6218..0e10d8aeffe1 100644
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/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);
-- 
2.30.2