netdev - RE: [PATCH net-next v2 1/2] qed: Add infrastructure for PTP support.

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Date:   Sun, 29 Jan 2017 17:26:13 +0000
From:   "Mintz, Yuval" <Yuval.Mintz@...ium.com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Kalluru, Sudarsana" <Sudarsana.Kalluru@...ium.com>
Subject: RE: [PATCH net-next v2 1/2] qed: Add infrastructure for PTP support.

> > +/* Read Rx timestamp */
> > +static int qed_ptp_hw_read_rx_ts(struct qed_dev *cdev, u64
> > +*timestamp) {
> > +	struct qed_hwfn *p_hwfn = QED_LEADING_HWFN(cdev);
> > +	struct qed_ptt *p_ptt = p_hwfn->p_ptp_ptt;
> > +	u32 val;
> > +
> > +	*timestamp = 0;
> > +	val = qed_rd(p_hwfn, p_ptt, NIG_REG_LLH_PTP_HOST_BUF_SEQID);
> > +	if (!(val & QED_TIMESTAMP_MASK)) {
> > +		DP_INFO(p_hwfn, "Invalid Rx timestamp, buf_seqid = %d\n",
> val);
> > +		return -EINVAL;
> > +	}
> > +
> > +	val = qed_rd(p_hwfn, p_ptt, NIG_REG_LLH_PTP_HOST_BUF_TS_LSB);
> > +	*timestamp = qed_rd(p_hwfn, p_ptt,
> NIG_REG_LLH_PTP_HOST_BUF_TS_MSB);
> 
> You can already "Reset timestamp register to allow new timestamp" at this
> point, before combining the MSB and LSB.

We could - but what difference would it make?

> > +	*timestamp <<= 32;
> > +	*timestamp |= val;
> > +
> > +	/* Reset timestamp register to allow new timestamp */
> > +	qed_wr(p_hwfn, p_ptt, NIG_REG_LLH_PTP_HOST_BUF_SEQID,
> > +	       QED_TIMESTAMP_MASK);
> > +
> > +	return 0;
> > +}