Re: [PATCH net-next] net: stmmac: fix mqprio and cbs combination

[Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>]

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On Oct 13, Daniel Machon wrote:
> Hi Lorenzo,
> 
> Just a question:
> 
> > The channel-mode mqprio offload and the CBS offload can currently not be
> > enabled at the same time. tc_mqprio_validate_chan_mode() refuses the
> > mqprio offload as soon as any TX queue is configured in AVB mode, and
> > tc_setup_cbs() refuses to enable CBS while the strict-priority scheduler
> > is active. As a result the combination is rejected whichever order the
> > two are configured in.
> > 
> > The strict-priority scheduler selected by the channel-mode mqprio
> > offload and the per-queue CBS shaper are independent MTL settings and do
> > not conflict, so drop the checks and let the combination be offloaded.
> > The following configuration, which was previously refused, now works:
> 
> Looks to me like these checks are shared by multiple cores. Are the MTL settings
> independent on all of them?

Can you please explain what you mean?
What I mean with this patch is we can have a given queue (e.g. queue X)
configured in MTL_QUEUE_AVB mode and another one (e.g. queue Y) configured
in MTL_QUEUE_DCB mode.

Regards,
Lorenzo

> 
> > 
> >   $ tc qdisc replace dev eth0 handle 100 parent root mqprio num_tc 4 \
> >         map  0  0  0  0  0  1  2  3  0  0  0  0  0  0  0  0 \
> >         queues 1@0 1@1 1@2 1@3 mode channel hw 1
> >   $ tc qdisc replace dev eth0 parent 100:2 handle 102: cbs \
> >         idleslope 800000 sendslope -1700000 hicredit 494 locredit -1049 offload 0
> >   $ tc qdisc replace dev eth0 parent 100:3 handle 103: cbs \
> >         idleslope 400000 sendslope -2100000 hicredit 247 locredit -1296 offload 1
> >   $ tc qdisc replace dev eth0 parent 100:4 handle 104: cbs \
> >         idleslope 200000 sendslope -2300000 hicredit 124 locredit -1419 offload 1
> > 
> > Fixes: 47891d501e34 ("net: stmmac: add tc mqprio hw queue priority offload")
> > Tested-by: Daniel Thompson <daniel@riscstar.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |  8 --------
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c   | 16 ----------------
> >  2 files changed, 24 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 56d89a696272..51d502930219 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -7740,14 +7740,6 @@ int stmmac_reinit_queues(struct net_device *dev, u8 rx_cnt, u8 tx_cnt)
> >  	    tx_cnt < priv->xmit_qdisc.num_tx_queues)
> >  		return -EINVAL;
> >  
> > -	if (priv->xmit_qdisc.prio_offload) {
> > -		for (i = priv->plat->tx_queues_to_use; i < tx_cnt; i++) {
> > -			if (priv->plat->tx_queues_cfg[i].mode_to_use ==
> > -			    MTL_QUEUE_AVB)
> > -				return -EINVAL;
> > -		}
> > -	}
> > -
> >  	if (netif_running(dev))
> >  		stmmac_release(dev);
> >  
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > index ea1f97d6f0bd..175236ba379d 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
> > @@ -346,9 +346,6 @@ static int tc_setup_cbs(struct stmmac_priv *priv,
> >  	if (!priv->dma_cap.av)
> >  		return -EOPNOTSUPP;
> >  
> > -	if (qopt->enable && priv->xmit_qdisc.prio_offload)
> > -		return -EOPNOTSUPP;
> > -
> >  	port_transmit_rate_kbps = qopt->idleslope - qopt->sendslope;
> >  
> >  	if (qopt->enable) {
> > @@ -1340,7 +1337,6 @@ static void tc_mqprio_config_queue_prio(struct stmmac_priv *priv,
> >  static int tc_mqprio_validate_chan_mode(struct stmmac_priv *priv,
> >  					struct tc_mqprio_qopt_offload *mqprio)
> >  {
> > -	struct plat_stmmacenet_data *pdata = priv->plat;
> >  	struct tc_mqprio_qopt *qopt = &mqprio->qopt;
> >  	int i;
> >  
> > @@ -1350,18 +1346,6 @@ static int tc_mqprio_validate_chan_mode(struct stmmac_priv *priv,
> >  		return -EOPNOTSUPP;
> >  	}
> >  
> > -	/* Forcing strict priority conflicts with the CBS algorithm
> > -	 * of AVB queues, so reject the offload when any queue is
> > -	 * configured as AVB.
> > -	 */
> > -	for (i = 0; i < pdata->tx_queues_to_use; i++) {
> > -		if (pdata->tx_queues_cfg[i].mode_to_use == MTL_QUEUE_AVB) {
> > -			NL_SET_ERR_MSG_MOD(mqprio->extack,
> > -					   "SP conflicts with AVB queues");
> > -			return -EOPNOTSUPP;
> > -		}
> > -	}
> > -
> >  	for (i = 0; i < qopt->num_tc; i++) {
> >  		/* The offload switches the MTL scheduler to strict
> >  		 * priority, which only supports a 1:1 TC to TX queue
> > 
> > ---
> > base-commit: d0bd617658ddfa5a115e64d1ab687bf155f6331f
> > change-id: 20261012-stmmac-mqprio-cbs-combo-341f12749ce2
> > 
> > Best regards,
> > -- 
> > Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
> > 
> 
> /Daniel

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