linux-kernel - Re: [Patch v3 net-next 3/7] octeontx2-pf: ethtool fec mode support

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Date:   Thu, 4 Feb 2021 15:33:48 +0000
From:   Hariprasad Kelam <hkelam@...vell.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "willemdebruijn.kernel@...il.com" <willemdebruijn.kernel@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>,
        Linu Cherian <lcherian@...vell.com>,
        "Geethasowjanya Akula" <gakula@...vell.com>,
        Jerin Jacob Kollanukkaran <jerinj@...vell.com>,
        Subbaraya Sundeep Bhatta <sbhatta@...vell.com>
Subject: Re: [Patch v3 net-next 3/7] octeontx2-pf: ethtool fec mode support

Hi Jakub,

> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, February 3, 2021 6:42 AM
> To: Hariprasad Kelam <hkelam@...vell.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> davem@...emloft.net; willemdebruijn.kernel@...il.com;
> andrew@...n.ch; Sunil Kovvuri Goutham <sgoutham@...vell.com>; Linu
> Cherian <lcherian@...vell.com>; Geethasowjanya Akula
> <gakula@...vell.com>; Jerin Jacob Kollanukkaran <jerinj@...vell.com>;
> Subbaraya Sundeep Bhatta <sbhatta@...vell.com>
> Subject: [EXT] Re: [Patch v3 net-next 3/7] octeontx2-pf: ethtool fec mode
> support
> 
> On Mon, 1 Feb 2021 10:54:40 +0530 Hariprasad Kelam wrote:
> > From: Christina Jacob <cjacob@...vell.com>
> >
> > Add ethtool support to configure fec modes baser/rs and support to
> > fecth FEC stats from CGX as well PHY.
> >
> > Configure fec mode
> > 	- ethtool --set-fec eth0 encoding rs/baser/off/auto Query fec mode
> > 	- ethtool --show-fec eth0
> 
> > +	if (pfvf->linfo.fec) {
> > +		sprintf(data, "Fec Corrected Errors: ");
> > +		data += ETH_GSTRING_LEN;
> > +		sprintf(data, "Fec Uncorrected Errors: ");
> > +		data += ETH_GSTRING_LEN;
> 
> Once again, you can't dynamically hide stats. ethtool makes 3 separate
> system calls - to get the number of stats, get the names, and get the values. If
> someone changes the FEC config in between those user space dumping stats
> will get confused.
> 
Agreed. Will fix this in next version.
> > +	}
> >  }
> 
> > +static int otx2_get_fecparam(struct net_device *netdev,
> > +			     struct ethtool_fecparam *fecparam) {
> > +	struct otx2_nic *pfvf = netdev_priv(netdev);
> > +	struct cgx_fw_data *rsp;
> > +	const int fec[] = {
> > +		ETHTOOL_FEC_OFF,
> > +		ETHTOOL_FEC_BASER,
> > +		ETHTOOL_FEC_RS,
> > +		ETHTOOL_FEC_BASER | ETHTOOL_FEC_RS}; #define
> FEC_MAX_INDEX 3
> > +	if (pfvf->linfo.fec < FEC_MAX_INDEX)
> 
> This should be <
Agreed . Current code miss the "ETHTOOL_FEC_BASER | ETHTOOL_FEC_RS" condition,  will fix this in next version.
> 
> > +		fecparam->active_fec = fec[pfvf->linfo.fec];
> 
> 
> > +	rsp = otx2_get_fwdata(pfvf);
> > +	if (IS_ERR(rsp))
> > +		return PTR_ERR(rsp);
> > +
> > +	if (rsp->fwdata.supported_fec <= FEC_MAX_INDEX) {
> > +		if (!rsp->fwdata.supported_fec)
> > +			fecparam->fec = ETHTOOL_FEC_NONE;
> > +		else
> > +			fecparam->fec = fec[rsp->fwdata.supported_fec];
> > +	}
> > +	return 0;
> > +}
> > +
> > +static int otx2_set_fecparam(struct net_device *netdev,
> > +			     struct ethtool_fecparam *fecparam) {
> > +	struct otx2_nic *pfvf = netdev_priv(netdev);
> > +	struct mbox *mbox = &pfvf->mbox;
> > +	struct fec_mode *req, *rsp;
> > +	int err = 0, fec = 0;
> > +
> > +	switch (fecparam->fec) {
> > +	/* Firmware does not support AUTO mode consider it as FEC_NONE
> */
> > +	case ETHTOOL_FEC_OFF:
> > +	case ETHTOOL_FEC_AUTO:
> > +	case ETHTOOL_FEC_NONE:
> 
> I _think_ NONE is for drivers to report that they don't support FEC settings.
> It's an output only parameter. On input OFF should be used.
> 
Thanks for pointing this.  Cross checked code also  _NONE is output is only parameter.
Will fix in next version.

> > +		fec = OTX2_FEC_NONE;
> > +		break;
> > +	case ETHTOOL_FEC_RS:
> > +		fec = OTX2_FEC_RS;
> > +		break;
> > +	case ETHTOOL_FEC_BASER:
> > +		fec = OTX2_FEC_BASER;
> > +		break;
> > +	default:
> > +		netdev_warn(pfvf->netdev, "Unsupported FEC mode: %d",
> > +			    fecparam->fec);
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (fec == pfvf->linfo.fec)
> > +		return 0;
> > +
> > +	mutex_lock(&mbox->lock);
> > +	req = otx2_mbox_alloc_msg_cgx_set_fec_param(&pfvf->mbox);
> > +	if (!req) {
> > +		err = -ENOMEM;
> > +		goto end;
> > +	}
> > +	req->fec = fec;
> > +	err = otx2_sync_mbox_msg(&pfvf->mbox);
> > +	if (err)
> > +		goto end;
> > +
> > +	rsp = (struct fec_mode *)otx2_mbox_get_rsp(&pfvf->mbox.mbox,
> > +						   0, &req->hdr);
> > +	if (rsp->fec >= 0) {
> > +		pfvf->linfo.fec = rsp->fec;
> > +		/* clear stale counters */
> > +		pfvf->hw.cgx_fec_corr_blks = 0;
> > +		pfvf->hw.cgx_fec_uncorr_blks = 0;
> 
> Stats are supposed to be cumulative. Don't reset the stats just because
> someone changed the FEC mode. You can miss errors this way.
>
Thanks for pointing this. Will fix in next version.

Thanks,
Hariprasad k 
> > +	} else {
> > +		err = rsp->fec;
> > +	}