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From: Bharat Bhushan <bbhushan2@marvell.com>
To: Simon Horman <horms@kernel.org>
CC: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sunil Kovvuri
 Goutham <sgoutham@marvell.com>,
        Geethasowjanya Akula <gakula@marvell.com>,
        Subbaraya Sundeep Bhatta <sbhatta@marvell.com>,
        Hariprasad Kelam
	<hkelam@marvell.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org"
	<kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        Jerin Jacob
	<jerinj@marvell.com>, Linu Cherian <lcherian@marvell.com>,
        "richardcochran@gmail.com" <richardcochran@gmail.com>
Subject: RE: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
 backpressure between CPT and NIX
Thread-Topic: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
 backpressure between CPT and NIX
Thread-Index: AQHapSQKuOy9XZhP3kiH1e4gTcWZRbGVVxCAgADtLRCAAEgEgIAABgbQ
Date: Tue, 14 May 2024 11:26:54 +0000
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Please see inline

> -----Original Message-----
> From: Simon Horman <horms@kernel.org>
> Sent: Tuesday, May 14, 2024 4:11 PM
> To: Bharat Bhushan <bbhushan2@marvell.com>
> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil Kovvuri
> Goutham <sgoutham@marvell.com>; Geethasowjanya Akula
> <gakula@marvell.com>; Subbaraya Sundeep Bhatta <sbhatta@marvell.com>;
> Hariprasad Kelam <hkelam@marvell.com>; davem@davemloft.net;
> edumazet@google.com; kuba@kernel.org; pabeni@redhat.com; Jerin Jacob
> <jerinj@marvell.com>; Linu Cherian <lcherian@marvell.com>;
> richardcochran@gmail.com
> Subject: Re: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
> backpressure between CPT and NIX
>=20
> On Tue, May 14, 2024 at 06:39:45AM +0000, Bharat Bhushan wrote:
> > Please see inline
> >
> > > -----Original Message-----
> > > From: Simon Horman <horms@kernel.org>
> > > Sent: Monday, May 13, 2024 9:45 PM
> > > To: Bharat Bhushan <bbhushan2@marvell.com>
> > > Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil
> > > Kovvuri Goutham <sgoutham@marvell.com>; Geethasowjanya Akula
> > > <gakula@marvell.com>; Subbaraya Sundeep Bhatta
> > > <sbhatta@marvell.com>; Hariprasad Kelam <hkelam@marvell.com>;
> > > davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> > > pabeni@redhat.com; Jerin Jacob <jerinj@marvell.com>; Linu Cherian
> > > <lcherian@marvell.com>; richardcochran@gmail.com
> > > 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<=3D>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@marvell.com>
> > >
> > > ...
> > >
> > > > 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 =3D &nix_hw->bp;
> > > >  	chan_base =3D pfvf->rx_chan_base + req->chan_base;
> > > >  	for (chan =3D chan_base; chan < (chan_base + req->chan_cnt); chan=
++) {
> > > > -		cfg =3D 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 =3D chan | BIT(11);
> > > > +		else
> > > > +			chan_v =3D 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 =3D 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 =3D=3D 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 =3D otx2_mbox_alloc_msg_nix_cpt_bp_enable(&pfvf-
> > > >mbox);
> > > > +	else
> > > > +		req =3D otx2_mbox_alloc_msg_nix_cpt_bp_disable(&pfvf-
> > > >mbox);
> > > > +
> > > > +	if (!req)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	req->chan_base =3D 0;
> > > > +#ifdef CONFIG_DCB
> > > > +	req->chan_cnt =3D pfvf->pfc_en ? IEEE_8021QAZ_MAX_TCS : 1;
> > > > +	req->bpid_per_chan =3D pfvf->pfc_en ? 1 : 0; #else
> > > > +	req->chan_cnt =3D  1;
> > > > +	req->bpid_per_chan =3D 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:
>=20
> Thanks. Just to clarify, my first suggestion was to move pfc_en outside o=
f
> CONFIG_DCB in otx2_nic.
>=20
> >
> > static bool is_pfc_enabled(struct otx2_nic *pfvf) { #ifdef CONFIG_DCB
> >         return pfvf->pfc_en ? true : false;
>=20
> FWIIW, I think this could also be:
>=20
> 	return !!pfvf->pfc_en;
>=20
> > #endif
> >         return false;
> > }
>=20
> Also, I do wonder if the following can work:
>=20
> 	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

>=20
> >
> > Using same like..
> > ...
> >         if (is_pfc_enabled(pfvf)) {
>=20
> If so, perhaps this can work:
>=20
> 	if (IS_ENABLED(CONFIG_DCB) && pfvf->pfc_en) {
> 		...
>=20
> >                 req->chan_cnt =3D IEEE_8021QAZ_MAX_TCS;
> >                 req->bpid_per_chan =3D 1;
> >         } else {
> >                 req->chan_cnt =3D 1;
> >                 req->bpid_per_chan =3D 0;
> >         }
> > ...