Re: [Intel-wired-lan] [PATCH iwl-next v3] igc: Change Tx mode for MQPRIO offloading

["Abdul Rahim, Faizal" <faizal.abdul.rahim@linux.intel.com>]

On 3/3/2025 5:16 pm, Kurt Kanzenbach wrote:
> The current MQPRIO offload implementation uses the legacy TSN Tx mode. In
> this mode the hardware uses four packet buffers and considers queue
> priorities.
> 
> In order to harmonize the TAPRIO implementation with MQPRIO, switch to the
> regular TSN Tx mode. This mode also uses four packet buffers and considers
> queue priorities. In addition to the legacy mode, transmission is always
> coupled to Qbv. The driver already has mechanisms to use a dummy schedule
> of 1 second with all gates open for ETF. Simply use this for MQPRIO too.
> 
> This reduces code and makes it easier to add support for frame preemption
> later.
> 
> While at it limit the netdev_tc calls to MQPRIO only.
> 
> Tested on i225 with real time application using high priority queue, iperf3
> using low priority queue and network TAP device.
> 
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
> ---
> Changes in v3:
> - Commit message (Paul)
> - Link to v2: https://lore.kernel.org/r/20250224-igc_mqprio_tx_mode-v2-1-9666da13c8d8@linutronix.de
> 
> Changes in v2:
> - Add comma to commit message (Faizal)
> - Simplify if condition (Faizal)
> - Link to v1: https://lore.kernel.org/r/20250217-igc_mqprio_tx_mode-v1-1-3a402fe1f326@linutronix.de
> ---
>   drivers/net/ethernet/intel/igc/igc.h      |  4 +---
>   drivers/net/ethernet/intel/igc/igc_main.c | 18 +++++++++++++-
>   drivers/net/ethernet/intel/igc/igc_tsn.c  | 40 ++-----------------------------
>   3 files changed, 20 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> index cd1d7b6c1782352094f6867a31b6958c929bbbf4..16d85bdf55a7e9c412c47acf727bca6bc7154c61 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -388,11 +388,9 @@ extern char igc_driver_name[];
>   #define IGC_FLAG_RX_LEGACY		BIT(16)
>   #define IGC_FLAG_TSN_QBV_ENABLED	BIT(17)
>   #define IGC_FLAG_TSN_QAV_ENABLED	BIT(18)
> -#define IGC_FLAG_TSN_LEGACY_ENABLED	BIT(19)
>   
>   #define IGC_FLAG_TSN_ANY_ENABLED				\
> -	(IGC_FLAG_TSN_QBV_ENABLED | IGC_FLAG_TSN_QAV_ENABLED |	\
> -	 IGC_FLAG_TSN_LEGACY_ENABLED)
> +	(IGC_FLAG_TSN_QBV_ENABLED | IGC_FLAG_TSN_QAV_ENABLED)
>   
>   #define IGC_FLAG_RSS_FIELD_IPV4_UDP	BIT(6)
>   #define IGC_FLAG_RSS_FIELD_IPV6_UDP	BIT(7)
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 472f009630c98e60c7166ceb8d05cb094f6c837b..240b6075197fb1e61077a736ddf8f9e67c1ed5cd 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -6679,13 +6679,14 @@ static int igc_tsn_enable_mqprio(struct igc_adapter *adapter,
>   				 struct tc_mqprio_qopt_offload *mqprio)
>   {
>   	struct igc_hw *hw = &adapter->hw;
> -	int i;
> +	int err, i;
>   
>   	if (hw->mac.type != igc_i225)
>   		return -EOPNOTSUPP;
>   
>   	if (!mqprio->qopt.num_tc) {
>   		adapter->strict_priority_enable = false;
> +		netdev_reset_tc(adapter->netdev);
>   		goto apply;
>   	}
>   
> @@ -6716,6 +6717,21 @@ static int igc_tsn_enable_mqprio(struct igc_adapter *adapter,
>   	igc_save_mqprio_params(adapter, mqprio->qopt.num_tc,
>   			       mqprio->qopt.offset);
>   
> +	err = netdev_set_num_tc(adapter->netdev, adapter->num_tc);
> +	if (err)
> +		return err;
> +
> +	for (i = 0; i < adapter->num_tc; i++) {
> +		err = netdev_set_tc_queue(adapter->netdev, i, 1,
> +					  adapter->queue_per_tc[i]);
> +		if (err)
> +			return err;
> +	}
> +
> +	/* In case the card is configured with less than four queues. */
> +	for (; i < IGC_MAX_TX_QUEUES; i++)
> +		adapter->queue_per_tc[i] = i;
> +
>   	mqprio->qopt.hw = TC_MQPRIO_HW_OFFLOAD_TCS;
>   
>   apply:
> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
> index 1e44374ca1ffbb86e9893266c590f318984ef574..7c28f3e7bb576f0e6a21c883e934ede4d53096f4 100644
> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
> @@ -37,18 +37,13 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
>   {
>   	unsigned int new_flags = adapter->flags & ~IGC_FLAG_TSN_ANY_ENABLED;
>   
> -	if (adapter->taprio_offload_enable)
> -		new_flags |= IGC_FLAG_TSN_QBV_ENABLED;
> -
> -	if (is_any_launchtime(adapter))
> +	if (adapter->taprio_offload_enable || is_any_launchtime(adapter) ||
> +	    adapter->strict_priority_enable)
>   		new_flags |= IGC_FLAG_TSN_QBV_ENABLED;
>   
>   	if (is_cbs_enabled(adapter))
>   		new_flags |= IGC_FLAG_TSN_QAV_ENABLED;
>   
> -	if (adapter->strict_priority_enable)
> -		new_flags |= IGC_FLAG_TSN_LEGACY_ENABLED;
> -
>   	return new_flags;
>   }
>   
> @@ -157,16 +152,12 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
>   	wr32(IGC_QBVCYCLET_S, 0);
>   	wr32(IGC_QBVCYCLET, NSEC_PER_SEC);
>   
> -	/* Reset mqprio TC configuration. */
> -	netdev_reset_tc(adapter->netdev);
> -
>   	/* Restore the default Tx arbitration: Priority 0 has the highest
>   	 * priority and is assigned to queue 0 and so on and so forth.
>   	 */
>   	igc_tsn_tx_arb(adapter, queue_per_tc);
>   
>   	adapter->flags &= ~IGC_FLAG_TSN_QBV_ENABLED;
> -	adapter->flags &= ~IGC_FLAG_TSN_LEGACY_ENABLED;
>   
>   	return 0;
>   }
> @@ -206,37 +197,10 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
>   		igc_tsn_set_retx_qbvfullthreshold(adapter);
>   
>   	if (adapter->strict_priority_enable) {
> -		int err;
> -
> -		err = netdev_set_num_tc(adapter->netdev, adapter->num_tc);
> -		if (err)
> -			return err;
> -
> -		for (i = 0; i < adapter->num_tc; i++) {
> -			err = netdev_set_tc_queue(adapter->netdev, i, 1,
> -						  adapter->queue_per_tc[i]);
> -			if (err)
> -				return err;
> -		}
> -
> -		/* In case the card is configured with less than four queues. */
> -		for (; i < IGC_MAX_TX_QUEUES; i++)
> -			adapter->queue_per_tc[i] = i;
> -
>   		/* Configure queue priorities according to the user provided
>   		 * mapping.
>   		 */
>   		igc_tsn_tx_arb(adapter, adapter->queue_per_tc);
> -
> -		/* Enable legacy TSN mode which will do strict priority without
> -		 * any other TSN features.
> -		 */
> -		tqavctrl = rd32(IGC_TQAVCTRL);
> -		tqavctrl |= IGC_TQAVCTRL_TRANSMIT_MODE_TSN;
> -		tqavctrl &= ~IGC_TQAVCTRL_ENHANCED_QAV;
> -		wr32(IGC_TQAVCTRL, tqavctrl);
> -
> -		return 0;
>   	}
>   
>   	for (i = 0; i < adapter->num_tx_queues; i++) {
> 
> ---
> base-commit: f77f12010f67259bd0e1ad18877ed27c721b627a
> change-id: 20250214-igc_mqprio_tx_mode-22c19c564605
> 
> Best regards,

Acked-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>