netdev - RE: [EXT] Re: [PATCH 1/3] enetc: add hardware timestamping support

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Message-ID: <VI1PR0401MB2237FB387B3F5ABC70EE4285F8060@VI1PR0401MB2237.eurprd04.prod.outlook.com>
Date:   Mon, 20 May 2019 03:20:23 +0000
From:   "Y.b. Lu" <yangbo.lu@....com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH 1/3] enetc: add hardware timestamping support

Hi,

> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: Thursday, May 16, 2019 10:33 PM
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: netdev@...r.kernel.org; David Miller <davem@...emloft.net>; Claudiu
> Manoil <claudiu.manoil@....com>; Shawn Guo <shawnguo@...nel.org>; Rob
> Herring <robh+dt@...nel.org>; devicetree@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH 1/3] enetc: add hardware timestamping support
> 
> 
> On Thu, May 16, 2019 at 09:59:08AM +0000, Y.b. Lu wrote:
> 
> > +config FSL_ENETC_HW_TIMESTAMPING
> > +     bool "ENETC hardware timestamping support"
> > +     depends on FSL_ENETC || FSL_ENETC_VF
> > +     help
> > +       Enable hardware timestamping support on the Ethernet packets
> > +       using the SO_TIMESTAMPING API. Because the RX BD ring dynamic
> > +       allocation hasn't been supported and it's too expensive to use
> 
> s/it's/it is/

[Y.b. Lu] Will modify it. BTW, may I know what's the purpose of dropping single quote character? For searching, script checking, or something else?
If require to not use single quote character, I will also modify some other places in Kconfig messages.

> 
> > +       extended RX BDs if timestamping isn't used, the option was used
> > +       to control hardware timestamping/extended RX BDs to be enabled
> > +       or not.
> 
> ..., this option enables extended RX BDs in order to support hardware
> timestamping.

[Y.b. Lu] Will rephrase it.

> 
> >  static bool enetc_clean_tx_ring(struct enetc_bdr *tx_ring, int
> > napi_budget)  {
> >       struct net_device *ndev = tx_ring->ndev;
> > +     struct enetc_ndev_priv *priv = netdev_priv(ndev);
> >       int tx_frm_cnt = 0, tx_byte_cnt = 0;
> >       struct enetc_tx_swbd *tx_swbd;
> > +     union enetc_tx_bd *txbd;
> > +     bool do_tstamp;
> >       int i, bds_to_clean;
> > +     u64 tstamp = 0;
> 
> Please keep in reverse Christmas tree order as much as possible:
> 
>         union enetc_tx_bd *txbd;
>         int i, bds_to_clean;
>         bool do_tstamp;
>         u64 tstamp = 0;
> 
> >       i = tx_ring->next_to_clean;
> >       tx_swbd = &tx_ring->tx_swbd[i];
> >       bds_to_clean = enetc_bd_ready_count(tx_ring, i);
> >
> > +     do_tstamp = false;
> > +
> >       while (bds_to_clean && tx_frm_cnt < ENETC_DEFAULT_TX_WORK) {
> >               bool is_eof = !!tx_swbd->skb;
> >
> > +             if (unlikely(tx_swbd->check_wb)) {
> > +                     txbd = ENETC_TXBD(*tx_ring, i);
> > +
> > +                     if (!(txbd->flags & ENETC_TXBD_FLAGS_W))
> > +                             goto no_wb;
> > +
> > +                     if (tx_swbd->do_tstamp) {
> > +                             enetc_get_tx_tstamp(&priv->si->hw, txbd,
> > +                                                 &tstamp);
> > +                             do_tstamp = true;
> > +                     }
> > +             }
> > +no_wb:
> 
> This goto seems strange and unnecessary.  How about this instead?
> 
>                         if (txbd->flags & ENETC_TXBD_FLAGS_W &&
>                             tx_swbd->do_tstamp) {
>                                 enetc_get_tx_tstamp(&priv->si->hw, txbd,
> &tstamp);
>                                 do_tstamp = true;
>                         }
> 
> >               enetc_unmap_tx_buff(tx_ring, tx_swbd);
> >               if (is_eof) {
> > +                     if (unlikely(do_tstamp)) {
> > +                             enetc_tstamp_tx(tx_swbd->skb, tstamp);
> > +                             do_tstamp = false;
> > +                     }
> >                       napi_consume_skb(tx_swbd->skb, napi_budget);
> >                       tx_swbd->skb = NULL;
> >               }
> > @@ -167,6 +169,11 @@ struct enetc_cls_rule {
> >
> >  #define ENETC_MAX_BDR_INT    2 /* fixed to max # of available cpus */
> >
> > +enum enetc_hw_features {
> 
> This is a poor choice of name.  It sounds like it describes HW capabilities, but
> you use it to track whether a feature is requested at run time.
> 
> > +     ENETC_F_RX_TSTAMP       = BIT(0),
> > +     ENETC_F_TX_TSTAMP       = BIT(1),
> > +};
> > +
> >  struct enetc_ndev_priv {
> >       struct net_device *ndev;
> >       struct device *dev; /* dma-mapping device */ @@ -178,6 +185,7
> @@
> > struct enetc_ndev_priv {
> >       u16 rx_bd_count, tx_bd_count;
> >
> >       u16 msg_enable;
> > +     int hw_features;
> 
> This is also poorly named.  How about "tstamp_request" instead?
> 
> >
> >       struct enetc_bdr *tx_ring[16];
> >       struct enetc_bdr *rx_ring[16];
> 
> Thanks,
> Richard