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 02:39:24 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Arun Ramadoss <arun.ramadoss@...rochip.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        woojung.huh@...rochip.com, UNGLinuxDriver@...rochip.com,
        andrew@...n.ch, vivien.didelot@...il.com, f.fainelli@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, linux@...linux.org.uk,
        Tristram.Ha@...rochip.com, richardcochran@...il.com,
        ceggers@...i.de
Subject: Re: [Patch net-next v1 02/12] net: dsa: microchip: ptp: Initial
 hardware time stamping support

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;
> +}