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

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Date: Tue, 14 May 2024 06:39:45 +0000
From: Bharat Bhushan <bbhushan2@...vell.com>
To: Simon Horman <horms@...nel.org>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sunil Kovvuri
 Goutham <sgoutham@...vell.com>,
        Geethasowjanya Akula <gakula@...vell.com>,
        Subbaraya Sundeep Bhatta <sbhatta@...vell.com>,
        Hariprasad Kelam
	<hkelam@...vell.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org"
	<kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        Jerin Jacob
	<jerinj@...vell.com>, Linu Cherian <lcherian@...vell.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>
Subject: RE: [EXTERNAL] Re: [net-next,v2 3/8] octeontx2-af: Disable
 backpressure between CPT and NIX

Please see inline

> -----Original Message-----
> From: Simon Horman <horms@...nel.org>
> Sent: Monday, May 13, 2024 9:45 PM
> To: Bharat Bhushan <bbhushan2@...vell.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Sunil Kovvuri
> Goutham <sgoutham@...vell.com>; Geethasowjanya Akula
> <gakula@...vell.com>; Subbaraya Sundeep Bhatta <sbhatta@...vell.com>;
> Hariprasad Kelam <hkelam@...vell.com>; davem@...emloft.net;
> edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; Jerin Jacob
> <jerinj@...vell.com>; Linu Cherian <lcherian@...vell.com>;
> richardcochran@...il.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<=>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@...vell.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 = &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:

static bool is_pfc_enabled(struct otx2_nic *pfvf)
{
#ifdef CONFIG_DCB
        return pfvf->pfc_en ? true : false;
#endif
        return false;
}

Using same like..
..
        if (is_pfc_enabled(pfvf)) {
                req->chan_cnt = IEEE_8021QAZ_MAX_TCS;
                req->bpid_per_chan = 1;
        } else {
                req->chan_cnt = 1;
                req->bpid_per_chan = 0;
        }
..

Thanks
-Bharat

> 
> > +
> > +	return otx2_sync_mbox_msg(&pfvf->mbox);
> > +}
> > +EXPORT_SYMBOL(otx2_nix_cpt_config_bp);
> > +
> >  /* Mbox message handlers */
> >  void mbox_handler_cgx_stats(struct otx2_nic *pfvf,
> >  			    struct cgx_stats_rsp *rsp)
> 
> ...