RE: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable backpressure between CPT and NIX

[Bharat Bhushan]

Please see inline

> -----Original Message-----
> From: Simon Horman <horms@xxxxxxxxxx>
> Sent: Tuesday, May 14, 2024 4:11 PM
> To: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Sunil Kovvuri
> Goutham <sgoutham@xxxxxxxxxxx>; Geethasowjanya Akula
> <gakula@xxxxxxxxxxx>; Subbaraya Sundeep Bhatta <sbhatta@xxxxxxxxxxx>;
> Hariprasad Kelam <hkelam@xxxxxxxxxxx>; davem@xxxxxxxxxxxxx;
> edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; Jerin Jacob
> <jerinj@xxxxxxxxxxx>; Linu Cherian <lcherian@xxxxxxxxxxx>;
> richardcochran@xxxxxxxxx
> Subject: Re: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
> backpressure between CPT and NIX
> 
> On Tue, May 14, 2024 at 06:39:45AM +0000, Bharat Bhushan wrote:
> > Please see inline
> >
> > > -----Original Message-----
> > > From: Simon Horman <horms@xxxxxxxxxx>
> > > Sent: Monday, May 13, 2024 9:45 PM
> > > To: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
> > > Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Sunil
> > > Kovvuri Goutham <sgoutham@xxxxxxxxxxx>; Geethasowjanya Akula
> > > <gakula@xxxxxxxxxxx>; Subbaraya Sundeep Bhatta
> > > <sbhatta@xxxxxxxxxxx>; Hariprasad Kelam <hkelam@xxxxxxxxxxx>;
> > > davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> > > pabeni@xxxxxxxxxx; Jerin Jacob <jerinj@xxxxxxxxxxx>; Linu Cherian
> > > <lcherian@xxxxxxxxxxx>; richardcochran@xxxxxxxxx
> > > Subject: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
> > > backpressure between CPT and NIX
> > >
> > >
> > > --------------------------------------------------------------------
> > > -- On Mon, May 13, 2024 at 04:24:41PM +0530, Bharat Bhushan wrote:
> > > > NIX can assert backpressure to CPT on the NIX<=>CPT link.
> > > > Keep the backpressure disabled for now. NIX block anyways handles
> > > > backpressure asserted by MAC due to PFC or flow control pkts.
> > > >
> > > > Signed-off-by: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
> > >
> > > ...
> > >
> > > > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > > b/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > >
> > > ...
> > >
> > > > @@ -592,8 +596,16 @@ int rvu_mbox_handler_nix_bp_disable(struct
> > > > rvu
> > > *rvu,
> > > >  	bp = &nix_hw->bp;
> > > >  	chan_base = pfvf->rx_chan_base + req->chan_base;
> > > >  	for (chan = chan_base; chan < (chan_base + req->chan_cnt); chan++) {
> > > > -		cfg = rvu_read64(rvu, blkaddr,
> > > NIX_AF_RX_CHANX_CFG(chan));
> > > > -		rvu_write64(rvu, blkaddr, NIX_AF_RX_CHANX_CFG(chan),
> > > > +		/* CPT channel for a given link channel is always
> > > > +		 * assumed to be BIT(11) set in link channel.
> > > > +		 */
> > > > +		if (cpt_link)
> > > > +			chan_v = chan | BIT(11);
> > > > +		else
> > > > +			chan_v = chan;
> > >
> > > Hi Bharat,
> > >
> > > The chan_v logic above seems to appear twice in this patch.
> > > I'd suggest adding a helper.
> >
> > Will fix in next version.
> >
> > >
> > > > +
> > > > +		cfg = rvu_read64(rvu, blkaddr,
> > > NIX_AF_RX_CHANX_CFG(chan_v));
> > > > +		rvu_write64(rvu, blkaddr, NIX_AF_RX_CHANX_CFG(chan_v),
> > > >  			    cfg & ~BIT_ULL(16));
> > > >
> > > >  		if (type == NIX_INTF_TYPE_LBK) {
> > >
> > > ...
> > >
> > > > diff --git
> > > > a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > > b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > > > index 7ec99c8d610c..e9d2e039a322 100644
> > > > --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > > > +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> > > > @@ -1705,6 +1705,31 @@ int otx2_nix_config_bp(struct otx2_nic
> > > > *pfvf,
> > > bool enable)
> > > >  }
> > > >  EXPORT_SYMBOL(otx2_nix_config_bp);
> > > >
> > > > +int otx2_nix_cpt_config_bp(struct otx2_nic *pfvf, bool enable) {
> > > > +	struct nix_bp_cfg_req *req;
> > > > +
> > > > +	if (enable)
> > > > +		req = otx2_mbox_alloc_msg_nix_cpt_bp_enable(&pfvf-
> > > >mbox);
> > > > +	else
> > > > +		req = otx2_mbox_alloc_msg_nix_cpt_bp_disable(&pfvf-
> > > >mbox);
> > > > +
> > > > +	if (!req)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	req->chan_base = 0;
> > > > +#ifdef CONFIG_DCB
> > > > +	req->chan_cnt = pfvf->pfc_en ? IEEE_8021QAZ_MAX_TCS : 1;
> > > > +	req->bpid_per_chan = pfvf->pfc_en ? 1 : 0; #else
> > > > +	req->chan_cnt =  1;
> > > > +	req->bpid_per_chan = 0;
> > > > +#endif
> > >
> > > IMHO, inline #ifdefs reduce readability and reduce maintainability.
> > >
> > > Would it be possible to either:
> > >
> > > 1. Include the pfc_en field in struct otx2_nic and make
> > >    sure it is set to 0 if CONFIG_DCB is unset; or 2. Provide a
> > > wrapper that returns 0 if CONFIG_DCB is unset,
> > >    otherwise pfvf->pfc_en.
> > >
> > > I suspect 1 will have little downside and be easiest to implement.
> >
> > pfc_en is already a field of otx2_nic but under CONFIG_DCB. Will fix by
> adding a wrapper function like:
> 
> Thanks. Just to clarify, my first suggestion was to move pfc_en outside of
> CONFIG_DCB in otx2_nic.
> 
> >
> > static bool is_pfc_enabled(struct otx2_nic *pfvf) { #ifdef CONFIG_DCB
> >         return pfvf->pfc_en ? true : false;
> 
> FWIIW, I think this could also be:
> 
> 	return !!pfvf->pfc_en;
> 
> > #endif
> >         return false;
> > }
> 
> Also, I do wonder if the following can work:
> 
> 	return IS_ENABLED(CONFIG_DCB) && pfvf->pfc_en;

This is required at more than one place, so will keep wrapper function with this condition check.

Thanks
-Bharat

> 
> >
> > Using same like..
> > ...
> >         if (is_pfc_enabled(pfvf)) {
> 
> If so, perhaps this can work:
> 
> 	if (IS_ENABLED(CONFIG_DCB) && pfvf->pfc_en) {
> 		...
> 
> >                 req->chan_cnt = IEEE_8021QAZ_MAX_TCS;
> >                 req->bpid_per_chan = 1;
> >         } else {
> >                 req->chan_cnt = 1;
> >                 req->bpid_per_chan = 0;
> >         }
> > ...