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Date: Fri, 25 Mar 2022 08:50:12 +0200 From: Tomas Melin <tomas.melin@...sala.com> To: netdev@...r.kernel.org Cc: nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, Tomas Melin <tomas.melin@...sala.com> Subject: [PATCH] net: macb: Restart tx only if queue pointer is lagging commit 5ea9c08a8692 ("net: macb: restart tx after tx used bit read") added support for restarting transmission. Restarting tx does not work in case controller asserts TXUBR interrupt and TQBP is already at the end of the tx queue. In that situation, restarting tx will immediately cause assertion of another TXUBR interrupt. The driver will end up in an infinite interrupt loop which it cannot break out of. For cases where TQBP is at the end of the tx queue, instead only clear TXUBR interrupt. As more data gets pushed to the queue, transmission will resume. This issue was observed on a Xilinx Zynq based board. During stress test of the network interface, driver would get stuck on interrupt loop within seconds or minutes causing CPU to stall. Signed-off-by: Tomas Melin <tomas.melin@...sala.com> --- drivers/net/ethernet/cadence/macb_main.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 800d5ced5800..e475be29845c 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -1658,6 +1658,7 @@ static void macb_tx_restart(struct macb_queue *queue) unsigned int head = queue->tx_head; unsigned int tail = queue->tx_tail; struct macb *bp = queue->bp; + unsigned int head_idx, tbqp; if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE) queue_writel(queue, ISR, MACB_BIT(TXUBR)); @@ -1665,6 +1666,13 @@ static void macb_tx_restart(struct macb_queue *queue) if (head == tail) return; + tbqp = queue_readl(queue, TBQP) / macb_dma_desc_get_size(bp); + tbqp = macb_adj_dma_desc_idx(bp, macb_tx_ring_wrap(bp, tbqp)); + head_idx = macb_adj_dma_desc_idx(bp, macb_tx_ring_wrap(bp, head)); + + if (tbqp == head_idx) + return; + macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART)); } -- 2.35.1
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