Re: [PATCH net-next] net: microchip: lan743x: improve throughput with rx timestamp config

[Jacob Keller]

On 9/26/2023 8:56 AM, Vishvambar Panth S wrote:
> Currently all RX frames are timestamped which results in a performance
> penalty when timestamping is not needed.  The default is now being
> changed to not timestamp any Rx frames (HWTSTAMP_FILTER_NONE), but
> support has been added to allow changing the desired RX timestamping
> mode (HWTSTAMP_FILTER_ALL -  which was the previous setting,
> HWTSTAMP_FILTER_PTP_V2_EVENT, HWTSTAMP_FILTER_PTP_V2_SYNC and
> HWTSTAMP_FILTER_PTP_V2_DELAY_REQ are the supported options) using
> SIOCSHWTSTAMP. All settings were tested using the hwstamp_ctl application.
> It is also noted that ptp4l, when started, preconfigures the device to
> timestamp using HWTSTAMP_FILTER_PTP_V2_EVENT, so this driver continues
> to work properly "out of the box".
> 
> Test setup:  x64 PC with LAN7430 ---> x64 PC as partner
> 

I don't think I would bother to support HWTSTAMP_FILTER_PTP_V2_DELAY_REQ
or HWTSTAMP_FILTER_PTP_V2_SYNC as these are pretty historic and only
useful for hardware which can't do HWTSTAMP_FILTER_PTP_V2_EVENT.

> iperf3 with - Timestamp all incoming packets:
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-5.05   sec   517 MBytes   859 Mbits/sec    0    sender
> [  5]   0.00-5.00   sec   515 MBytes   864 Mbits/sec         receiver
> 
> iperf Done.
> 
> iperf3 with - Timestamp only PTP packets:
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-5.04   sec   563 MBytes   937 Mbits/sec    0    sender
> [  5]   0.00-5.00   sec   561 MBytes   941 Mbits/sec         receiver
> 
> 

Pretty significant cost here for the timestamping all frames. Makes
sense to leave the default to NONE unless requested.

Please find the earlier conversation at the link below
> Link: https://lore.kernel.org/all/20230731125418.75140-1-vishvambarpanth.s@xxxxxxxxxxxxx/
> 
> Signed-off-by: Vishvambar Panth S <vishvambarpanth.s@xxxxxxxxxxxxx>
> ---
>  .../net/ethernet/microchip/lan743x_ethtool.c  |  5 +-
>  drivers/net/ethernet/microchip/lan743x_main.c | 58 ++++++++++++++++++-
>  drivers/net/ethernet/microchip/lan743x_main.h |  8 +++
>  drivers/net/ethernet/microchip/lan743x_ptp.c  |  9 +++
>  4 files changed, 78 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microchip/lan743x_ethtool.c b/drivers/net/ethernet/microchip/lan743x_ethtool.c
> index 2db5949b4c7e..855844df5ea1 100644
> --- a/drivers/net/ethernet/microchip/lan743x_ethtool.c
> +++ b/drivers/net/ethernet/microchip/lan743x_ethtool.c
> @@ -1047,7 +1047,10 @@ static int lan743x_ethtool_get_ts_info(struct net_device *netdev,
>  			    BIT(HWTSTAMP_TX_ON) |
>  			    BIT(HWTSTAMP_TX_ONESTEP_SYNC);
>  	ts_info->rx_filters = BIT(HWTSTAMP_FILTER_NONE) |
> -			      BIT(HWTSTAMP_FILTER_ALL);
> +			      BIT(HWTSTAMP_FILTER_ALL) |
> +			      BIT(HWTSTAMP_FILTER_PTP_V2_EVENT) |
> +			      BIT(HWTSTAMP_FILTER_PTP_V2_SYNC) |
> +			      BIT(HWTSTAMP_FILTER_PTP_V2_DELAY_REQ);
>  	return 0;
>  }
>  
> diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
> index f940895b14e8..0389bc7cf603 100644
> --- a/drivers/net/ethernet/microchip/lan743x_main.c
> +++ b/drivers/net/ethernet/microchip/lan743x_main.c
> @@ -1870,6 +1870,63 @@ static int lan743x_tx_get_avail_desc(struct lan743x_tx *tx)
>  		return last_head - last_tail - 1;
>  }
>  
> +int lan743x_rx_set_tstamp_mode(struct lan743x_adapter *adapter,
> +			       int rx_filter)
> +{
> +	int channel_number;
> +	int index;
> +	u32 data;
> +
> +	switch (rx_filter) {
> +	case HWTSTAMP_FILTER_PTP_V2_SYNC:
> +			data = lan743x_csr_read(adapter, PTP_RX_TS_CFG);
> +			data &= ~PTP_RX_TS_CFG_EVENT_MSGS_;
> +			data |= PTP_RX_TS_CFG_SYNC_MSG_;
> +			lan743x_csr_write(adapter, PTP_RX_TS_CFG, data);
> +			break;
> +	case HWTSTAMP_FILTER_PTP_V2_DELAY_REQ:
> +			data = lan743x_csr_read(adapter, PTP_RX_TS_CFG);
> +			data &= ~PTP_RX_TS_CFG_EVENT_MSGS_;
> +			data |= PTP_RX_TS_CFG_DELAY_REQ_MSG_;
> +			lan743x_csr_write(adapter, PTP_RX_TS_CFG, data);
> +			break;
> +	case HWTSTAMP_FILTER_PTP_V2_EVENT:
> +			data = lan743x_csr_read(adapter, PTP_RX_TS_CFG);
> +			data |= PTP_RX_TS_CFG_EVENT_MSGS_;
> +			lan743x_csr_write(adapter, PTP_RX_TS_CFG, data);
> +			break;
> +	case HWTSTAMP_FILTER_NONE:
> +	case HWTSTAMP_FILTER_ALL:
> +			break;

At first this break was a bit confusing to me, since nothing is set here.

> +	default:
> +			netif_warn(adapter, drv, adapter->netdev,
> +				   "rx timestamp = %d is not supported\n",
> +				   rx_filter);
> +			return -EINVAL;
> +	}
> +
> +	for (index = 0; index < LAN743X_USED_RX_CHANNELS; index++) {
> +		channel_number = adapter->rx[index].channel_number;
> +		data = lan743x_csr_read(adapter, RX_CFG_B(channel_number));
> +		if (rx_filter == HWTSTAMP_FILTER_NONE) {
> +			data &= ~(RX_CFG_B_TS_ALL_RX_ |
> +				  RX_CFG_B_TS_DESCR_EN_);
> +		} else if (rx_filter == HWTSTAMP_FILTER_ALL) {
> +			data |= RX_CFG_B_TS_ALL_RX_;
> +		} else {
> +			/* enable storing timestamping in extension descriptor
> +			 * instead of timestamping all the packets
> +			 */
> +			data &= ~RX_CFG_B_TS_ALL_RX_;
> +			data |= RX_CFG_B_TS_DESCR_EN_;
> +		}

I might have made the decision of what to program in the switch case
above and then done the write here with "data &= ~MASK; data |= setting"
rather than having two separate decision points.

> +		lan743x_csr_write(adapter, RX_CFG_B(channel_number),
> +				  data);
> +	}
> +
> +	return 0;
> +}
> +

Rest of the code seems fine, and the implementation looks ok.

I'd suggest dropping the not so useful timestamp filters for only sync
or only delay request, keeping only V2_EVENT, but either way:

Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>