6.12-stable review patch. If anyone has any objections, please let me know.
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From: Siddharth Vadapalli s-vadapalli@ti.com
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: stable@vger.kernel.org Signed-off-by: Siddharth Vadapalli s-vadapalli@ti.com Link: https://patch.msgid.link/20241220075618.228202-1-s-vadapalli@ti.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c @@ -3525,7 +3525,7 @@ static int am65_cpsw_nuss_probe(struct p init_completion(&common->tdown_complete); common->tx_ch_num = AM65_CPSW_DEFAULT_TX_CHNS; common->rx_ch_num_flows = AM65_CPSW_DEFAULT_RX_CHN_FLOWS; - 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,