From 14065738fc11942bd2ffcb4f48722c2e59a304fc Mon Sep 17 00:00:00 2001 From: Siddharth Vadapalli Date: Fri, 20 Dec 2024 13:26:14 +0530 Subject: [PATCH] net: ethernet: ti: am65-cpsw: default to round-robin for host port receive BugLink: https://bugs.launchpad.net/bugs/2106632 commit 4a4d38ace1fb0586bffd2aab03caaa05d6011748 upstream. The Host Port (i.e. CPU facing port) of CPSW receives traffic from Linux via TX DMA Channels which are Hardware Queues consisting of traffic categorized according to their priority. The Host Port is configured to dequeue traffic from these Hardware Queues on the basis of priority i.e. as long as traffic exists on a Hardware Queue of a higher priority, the traffic on Hardware Queues of lower priority isn't dequeued. An alternate operation is also supported wherein traffic can be dequeued by the Host Port in a Round-Robin manner. Until commit under Fixes, the am65-cpsw driver enabled a single TX DMA Channel, due to which, unless modified by user via "ethtool", all traffic from Linux is transmitted on DMA Channel 0. Therefore, configuring the Host Port for priority based dequeuing or Round-Robin operation is identical since there is a single DMA Channel. Since commit under Fixes, all 8 TX DMA Channels are enabled by default. Additionally, the default "tc mapping" doesn't take into account the possibility of different traffic profiles which various users might have. This results in traffic starvation at the Host Port due to the priority based dequeuing which has been enabled by default since the inception of the driver. The traffic starvation triggers NETDEV WATCHDOG timeout for all TX DMA Channels that haven't been serviced due to the presence of traffic on the higher priority TX DMA Channels. Fix this by defaulting to Round-Robin dequeuing at the Host Port, which shall ensure that traffic is dequeued from all TX DMA Channels irrespective of the traffic profile. This will address the NETDEV WATCHDOG timeouts. At the same time, users can still switch from Round-Robin to Priority based dequeuing at the Host Port with the help of the "p0-rx-ptype-rrobin" private flag of "ethtool". Users are expected to setup an appropriate "tc mapping" that suits their traffic profile when switching to priority based dequeuing at the Host Port. Fixes: be397ea3473d ("net: ethernet: am65-cpsw: Set default TX channels to maximum") Cc: Signed-off-by: Siddharth Vadapalli Link: https://patch.msgid.link/20241220075618.228202-1-s-vadapalli@ti.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Signed-off-by: Manuel Diewald Signed-off-by: Mehmet Basaran --- drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c index 1d00e21808c1..a5ac7b9223da 100644 --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c @@ -2994,7 +2994,7 @@ static int am65_cpsw_nuss_probe(struct platform_device *pdev) common->rx_flow_id_base = -1; init_completion(&common->tdown_complete); common->tx_ch_num = AM65_CPSW_DEFAULT_TX_CHNS; - common->pf_p0_rx_ptype_rrobin = false; + common->pf_p0_rx_ptype_rrobin = true; common->default_vlan = 1; common->ports = devm_kcalloc(dev, common->port_num,