Re: [PATCH iwl-next 9/9] igc: Add support to get frame preemption statistics via ethtool

[Vladimir Oltean <olteanv@gmail.com>]

On Mon, Dec 16, 2024 at 01:47:20AM -0500, Faizal Rahim wrote:
> Implemented "ethtool --include-statistics --show-mm" callback for IGC.
> 
> Tested preemption scenario to check preemption statistics:
> 1) Trigger verification handshake on both boards:
>     $ sudo ethtool --set-mm enp1s0 pmac-enabled on
>     $ sudo ethtool --set-mm enp1s0 tx-enabled on
>     $ sudo ethtool --set-mm enp1s0 verify-enabled on
> 2) Set preemptible or express queue in taprio for tx board:
>     $ sudo tc qdisc replace dev enp1s0 parent root handle 100 taprio \
>       num_tc 4 map 0 1 2 3 0 0 0 0 0 0 0 0 0 0 0 0 \
>       queues 1@0 1@1 1@2 1@3 base-time 0 sched-entry S F 100000 \
>       fp E E P P

Hmm, the prio_tc_map pattern changed since the last time I looked at igc
examples? It was in decreasing order before? How do you handle backwards
compatibility with the Tx ring strict priority default configuration?
I haven't downloaded the entire set locally, will do so later.

> 3) Send large size packets on preemptible queue
> 4) Send small size packets on express queue to preempt packets in
>    preemptible queue
> 5) Show preemption statistics on the receiving board:
>    $ ethtool --include-statistics --show-mm enp1s0
>      MAC Merge layer state for enp1s0:
>      pMAC enabled: on
>      TX enabled: on
>      TX active: on
>      TX minimum fragment size: 252
>      RX minimum fragment size: 252
>      Verify enabled: on
>      Verify time: 128
>      Max verify time: 128
>      Verification status: SUCCEEDED
>      Statistics:
>      	MACMergeFrameAssErrorCount: 0
> 	MACMergeFrameSmdErrorCount: 0
> 	MACMergeFrameAssOkCount: 511
> 	MACMergeFragCountRx: 764
> 	MACMergeFragCountTx: 0
> 	MACMergeHoldCount: 0
> 
> Co-developed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_ethtool.c | 40 ++++++++++++++++++++
>  drivers/net/ethernet/intel/igc/igc_regs.h    | 19 ++++++++++
>  2 files changed, 59 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_ethtool.c b/drivers/net/ethernet/intel/igc/igc_ethtool.c
> index 16aa6e4e1727..90a9dbb0d901 100644
> --- a/drivers/net/ethernet/intel/igc/igc_ethtool.c
> +++ b/drivers/net/ethernet/intel/igc/igc_ethtool.c
> @@ -1835,6 +1835,45 @@ static int igc_ethtool_set_mm(struct net_device *netdev,
>  	return igc_tsn_offload_apply(adapter);
>  }
>  
> +/**
> + * igc_ethtool_get_frame_ass_error - Get the frame assembly error count.
> + * @dev: Pointer to the net_device structure.
> + * @return: The count of frame assembly errors.

I may be wrong, but I think the syntax for kernel-doc is "Returns: "

> + */
> +static u64 igc_ethtool_get_frame_ass_error(struct net_device *dev)
> +{
> +	struct igc_adapter *adapter = netdev_priv(dev);
> +	u32 ooo_smdc, ooo_frame_cnt, ooo_frag_cnt; /* Out of order statistics */
> +	struct igc_hw *hw = &adapter->hw;
> +	u32 miss_frame_frag_cnt;
> +	u32 reg_value;
> +
> +	reg_value = rd32(IGC_PRMEXPRCNT);
> +	ooo_smdc = reg_value & IGC_PRMEXPRCNT_OOO_SMDC;
> +	ooo_frame_cnt = (reg_value & IGC_PRMEXPRCNT_OOO_FRAME_CNT)
> +			 >> IGC_PRMEXPRCNT_OOO_FRAME_CNT_SHIFT;
> +	ooo_frag_cnt = (reg_value & IGC_PRMEXPRCNT_OOO_FRAG_CNT)
> +			>> IGC_PRMEXPRCNT_OOO_FRAG_CNT_SHIFT;
> +	miss_frame_frag_cnt = (reg_value & IGC_PRMEXPRCNT_MISS_FRAME_FRAG_CNT)
> +			      >> IGC_PRMEXPRCNT_MISS_FRAME_FRAG_CNT_SHIFT;

Candidates for FIELD_GET()?

> +
> +	return ooo_smdc + ooo_frame_cnt + ooo_frag_cnt + miss_frame_frag_cnt;
> +}
> +
> +static void igc_ethtool_get_mm_stats(struct net_device *dev,
> +				     struct ethtool_mm_stats *stats)
> +{
> +	struct igc_adapter *adapter = netdev_priv(dev);
> +	struct igc_hw *hw = &adapter->hw;
> +
> +	stats->MACMergeFrameAssErrorCount = igc_ethtool_get_frame_ass_error(dev);
> +	stats->MACMergeFrameSmdErrorCount = 0; /* Not available in IGC */
> +	stats->MACMergeFrameAssOkCount = rd32(IGC_PRMPTDRCNT);
> +	stats->MACMergeFragCountRx =  rd32(IGC_PRMEVNTRCNT);
> +	stats->MACMergeFragCountTx = rd32(IGC_PRMEVNTTCNT);
> +	stats->MACMergeHoldCount = 0; /* Not available in IGC */

Don't report counters as zero when in reality you don't know.

Just don't assign values to these. mm_prepare_data() -> ethtool_stats_init()
presets them to 0xffffffffffffffff (ETHTOOL_STAT_NOT_SET), and
mm_put_stats() -> mm_put_stat() detects whether they are still equal to
this value, and if they are, does not report netlink attributes for them.

> +}
> +
>  static int igc_ethtool_get_link_ksettings(struct net_device *netdev,
>  					  struct ethtool_link_ksettings *cmd)
>  {
> @@ -2124,6 +2163,7 @@ static const struct ethtool_ops igc_ethtool_ops = {
>  	.get_channels		= igc_ethtool_get_channels,
>  	.get_mm			= igc_ethtool_get_mm,
>  	.set_mm			= igc_ethtool_set_mm,
> +	.get_mm_stats		= igc_ethtool_get_mm_stats,
>  	.set_channels		= igc_ethtool_set_channels,
>  	.get_priv_flags		= igc_ethtool_get_priv_flags,
>  	.set_priv_flags		= igc_ethtool_set_priv_flags,
> diff --git a/drivers/net/ethernet/intel/igc/igc_regs.h b/drivers/net/ethernet/intel/igc/igc_regs.h
> index 12ddc5793651..f40946cce35a 100644
> --- a/drivers/net/ethernet/intel/igc/igc_regs.h
> +++ b/drivers/net/ethernet/intel/igc/igc_regs.h
> @@ -222,6 +222,25 @@
>  
>  #define IGC_FTQF(_n)	(0x059E0 + (4 * (_n)))  /* 5-tuple Queue Fltr */
>  
> +/* Time sync registers - preemption statistics */
> +#define IGC_PRMEVNTTCNT		0x04298	/* TX Preemption event counter */
> +#define IGC_PRMEVNTRCNT		0x0429C	/* RX Preemption event counter */
> +#define IGC_PRMPTDRCNT		0x04284	/* Good RX Preempted Packets */
> +
> + /* Preemption Exception Counter */
> +#define IGC_PRMEXPRCNT					0x042A0
> +/* Received out of order packets with SMD-C and NOT ReumeRx */
> +#define IGC_PRMEXPRCNT_OOO_SMDC 0x000000FF
> +/* Received out of order packets with SMD-C and wrong Frame CNT */
> +#define IGC_PRMEXPRCNT_OOO_FRAME_CNT			0x0000FF00
> +#define IGC_PRMEXPRCNT_OOO_FRAME_CNT_SHIFT		8
> +/* Received out of order packets with SMD-C and wrong Frag CNT */
> +#define IGC_PRMEXPRCNT_OOO_FRAG_CNT			0x00FF0000
> +#define IGC_PRMEXPRCNT_OOO_FRAG_CNT_SHIFT		16
> +/* Received packets with SMD-S and ReumeRx */

What is ReumeRx?

> +#define IGC_PRMEXPRCNT_MISS_FRAME_FRAG_CNT		0xFF000000
> +#define IGC_PRMEXPRCNT_MISS_FRAME_FRAG_CNT_SHIFT	24
> +
>  /* Transmit Scheduling Registers */
>  #define IGC_TQAVCTRL		0x3570
>  #define IGC_TXQCTL(_n)		(0x3344 + 0x4 * (_n))
> -- 
> 2.25.1
> 
>