netdev - Re: [Patch net-next v1 02/12] net: dsa: microchip: ptp: Initial hardware time stamping support

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Date:   Thu, 1 Dec 2022 10:17:35 +0000
From:   <Arun.Ramadoss@...rochip.com>
To:     <olteanv@...il.com>
CC:     <andrew@...n.ch>, <linux-kernel@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>, <vivien.didelot@...il.com>,
        <linux@...linux.org.uk>, <ceggers@...i.de>,
        <Tristram.Ha@...rochip.com>, <f.fainelli@...il.com>,
        <kuba@...nel.org>, <edumazet@...gle.com>, <pabeni@...hat.com>,
        <richardcochran@...il.com>, <netdev@...r.kernel.org>,
        <Woojung.Huh@...rochip.com>, <davem@...emloft.net>
Subject: Re: [Patch net-next v1 02/12] net: dsa: microchip: ptp: Initial
 hardware time stamping support

Hi Vladimir,

On Thu, 2022-12-01 at 02:39 +0200, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> On Mon, Nov 28, 2022 at 04:02:17PM +0530, Arun Ramadoss wrote:
> > diff --git a/drivers/net/dsa/microchip/ksz_common.h
> > b/drivers/net/dsa/microchip/ksz_common.h
> > index 5a6bfd42c6f9..cd20f39a565f 100644
> > --- a/drivers/net/dsa/microchip/ksz_common.h
> > +++ b/drivers/net/dsa/microchip/ksz_common.h
> > @@ -103,6 +103,10 @@ struct ksz_port {
> >       struct ksz_device *ksz_dev;
> >       struct ksz_irq pirq;
> >       u8 num;
> > +#if IS_ENABLED(CONFIG_NET_DSA_MICROCHIP_KSZ_PTP)
> > +     u8 hwts_tx_en;
> 
> Variable named "en" (enable) which takes the values 0 or 2? Not good.
> Also, why is the type not enum hwtstamp_tx_types, but u8? Can't you
> name
> this "enum hwtstamp_tx_types tx_type"?
> 
> > +     bool hwts_rx_en;
> > +#endif
> >  };

I will rename variable.

> > 
> >  struct ksz_device {
> > diff --git a/drivers/net/dsa/microchip/ksz_ptp.c
> > b/drivers/net/dsa/microchip/ksz_ptp.c
> > index c737635ca266..a41418c6adf6 100644
> > --- a/drivers/net/dsa/microchip/ksz_ptp.c
> > +++ b/drivers/net/dsa/microchip/ksz_ptp.c
> > @@ -36,15 +36,88 @@ int ksz_get_ts_info(struct dsa_switch *ds, int
> > port, struct ethtool_ts_info *ts)
> >                             SOF_TIMESTAMPING_RX_HARDWARE |
> >                             SOF_TIMESTAMPING_RAW_HARDWARE;
> > 
> > -     ts->tx_types = BIT(HWTSTAMP_TX_OFF);
> > +     ts->tx_types = BIT(HWTSTAMP_TX_OFF) |
> > BIT(HWTSTAMP_TX_ONESTEP_P2P);
> > 
> > -     ts->rx_filters = BIT(HWTSTAMP_FILTER_NONE);
> > +     ts->rx_filters = BIT(HWTSTAMP_FILTER_NONE) |
> > BIT(HWTSTAMP_FILTER_ALL);
> > 
> >       ts->phc_index = ptp_clock_index(ptp_data->clock);
> > 
> >       return 0;
> >  }
> > 
> > +int ksz_hwtstamp_get(struct dsa_switch *ds, int port, struct ifreq
> > *ifr)
> > +{
> > +     struct ksz_device *dev = ds->priv;
> > +     struct hwtstamp_config config;
> > +
> > +     config.flags = 0;
> > +
> > +     config.tx_type = dev->ports[port].hwts_tx_en;
> > +
> > +     if (dev->ports[port].hwts_rx_en)
> > +             config.rx_filter = HWTSTAMP_FILTER_ALL;
> > +     else
> > +             config.rx_filter = HWTSTAMP_FILTER_NONE;
> > +
> > +     return copy_to_user(ifr->ifr_data, &config, sizeof(config)) ?
> > +             -EFAULT : 0;
> > +}
> > +
> > +static int ksz_set_hwtstamp_config(struct ksz_device *dev, int
> > port,
> > +                                struct hwtstamp_config *config)
> > +{
> > +     struct ksz_port *prt = &dev->ports[port];
> > +
> > +     if (config->flags)
> > +             return -EINVAL;
> > +
> > +     switch (config->tx_type) {
> > +     case HWTSTAMP_TX_OFF:
> > +     case HWTSTAMP_TX_ONESTEP_P2P:
> > +             prt->hwts_tx_en = config->tx_type;
> > +             break;
> > +     default:
> > +             return -ERANGE;
> > +     }
> > +
> > +     switch (config->rx_filter) {
> > +     case HWTSTAMP_FILTER_NONE:
> > +             prt->hwts_rx_en = false;
> > +             break;
> > +     default:
> > +             prt->hwts_rx_en = true;
> > +             break;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +int ksz_hwtstamp_set(struct dsa_switch *ds, int port, struct ifreq
> > *ifr)
> > +{
> > +     struct ksz_device *dev = ds->priv;
> > +     struct ksz_ptp_data *ptp_data;
> > +     struct hwtstamp_config config;
> > +     int ret;
> > +
> > +     ptp_data = &dev->ptp_data;
> > +
> > +     mutex_lock(&ptp_data->lock);
> 
> I'm not sure that this mutex serves any purpose at all?
> 
> One could have argued that concurrent calls to ksz_hwtstamp_get()
> shouldn't be able to see incoherent values of prt->hwts_tx_en and of
> prt->hwts_rx_en.
> 
> But ksz_hwtstamp_get() doesn't acquire this mutex, so that is not
> true,
> this isn't why the mutex is acquired here. I don't know why it is.

Mutex is not needed. I will remove it.

> 
> > +
> > +     ret = copy_from_user(&config, ifr->ifr_data, sizeof(config));
> > +     if (ret)
> > +             goto error_return;
> > +
> > +     ret = ksz_set_hwtstamp_config(dev, port, &config);
> > +     if (ret)
> > +             goto error_return;
> > +
> > +     ret = copy_to_user(ifr->ifr_data, &config, sizeof(config));
> > +
> > +error_return:
> > +     mutex_unlock(&ptp_data->lock);
> > +     return ret;
> > +}