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

Vladimir Oltean
2022-12-01T00:39:32Z

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
> };
>
> 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.

> +
> + 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;
> +}