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SubjectRe: [PATCH] staging: fsl-dpaa2/eth: Add support for hardware timestamping
On Wed, Apr 25, 2018 at 05:17:49PM +0800, Yangbo Lu wrote:
> @@ -275,6 +278,16 @@ static void dpaa2_eth_rx(struct dpaa2_eth_priv *priv,
>
> prefetch(skb->data);
>
> + /* Get the timestamp value */
> + if (priv->ts_rx_en) {
> + struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
> + u64 *ns = dpaa2_get_ts(vaddr, false);
> +
> + *ns = DPAA2_PTP_NOMINAL_FREQ_PERIOD_NS * le64_to_cpup(ns);

This will cause Sparse endianess warnings.

I don't totally understand why we're writing to *ns. Do we access *ns
again or not? Either way, this doesn't seem right. In other words, why
don't we do this:

__le64 *period = dpaa2_get_ts(vaddr, false);
u64 ns;

ns = DPAA2_PTP_NOMINAL_FREQ_PERIOD_NS * le64_to_cpup(period);
memset(shhwtstamps, 0, sizeof(*shhwtstamps));
shhwtstamps->hwtstamp = ns_to_ktime(ns);

Then if we need to save a munged *ns then we can do this at the end:

/* we need this because blah blah blah */
*period = (__le64)ns;


> + memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> + shhwtstamps->hwtstamp = ns_to_ktime(*ns);
> + }
> +
> /* Check if we need to validate the L4 csum */
> if (likely(dpaa2_fd_get_frc(fd) & DPAA2_FD_FRC_FASV)) {
> status = le32_to_cpu(fas->status);

[ snip ]

> @@ -520,6 +561,19 @@ static void free_tx_fd(const struct dpaa2_eth_priv *priv,
> return;
> }
>
> + /* Get the timestamp value */
> + if (priv->ts_tx_en && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
> + struct skb_shared_hwtstamps shhwtstamps;
> + u64 *ns;
> +
> + memset(&shhwtstamps, 0, sizeof(shhwtstamps));
> +
> + ns = dpaa2_get_ts(skbh, true);
> + *ns = DPAA2_PTP_NOMINAL_FREQ_PERIOD_NS * le64_to_cpup(ns);
> + shhwtstamps.hwtstamp = ns_to_ktime(*ns);
> + skb_tstamp_tx(skb, &shhwtstamps);

Sparse issues here also.

> + }
> +
> /* Free SGT buffer allocated on tx */
> if (fd_format != dpaa2_fd_single)
> skb_free_frag(skbh);
> @@ -552,6 +606,10 @@ static netdev_tx_t dpaa2_eth_tx(struct sk_buff *skb, struct net_device *net_dev)
> goto err_alloc_headroom;
> }
> percpu_extras->tx_reallocs++;
> +
> + if (skb->sk)
> + skb_set_owner_w(ns, skb->sk);

Is this really related? (I have not looked at this code).

> +
> dev_kfree_skb(skb);
> skb = ns;
> }

[ snip ]

> @@ -319,6 +351,9 @@ struct dpaa2_eth_priv {
> u16 bpid;
> struct iommu_domain *iommu_domain;
>
> + bool ts_tx_en; /* Tx timestamping enabled */
> + bool ts_rx_en; /* Rx timestamping enabled */

These variable names are not great. I wouldn't have understood "ts_"
without the comment. "tx_" is good. "en" is confusing until you read
the comment. But really it should just be left out because "enable" is
assumed, generally. Last week I asked someone to rewrite a patch that
had a _disable variable because negative variables lead to double
negatives which screw with my tiny head.

if (blah_disable != 0) {

OH MY BLASTED WORD MY BRIAN ESPLODED!!!1!

So let's just name these "tx_timestamps" or something.


> +
> u16 tx_qdid;
> u16 rx_buf_align;
> struct fsl_mc_io *mc_io;
regards,
dan carpenter

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