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Message-ID: <20240328114633.GI403975@kernel.org>
Date: Thu, 28 Mar 2024 11:46:33 +0000
From: Simon Horman <horms@...nel.org>
To: Kurt Kanzenbach <kurt@...utronix.de>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Vinicius Costa Gomes <vinicius.gomes@...el.com>,
intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-next v2] igc: Add MQPRIO offload support
On Tue, Mar 26, 2024 at 02:34:54PM +0100, Kurt Kanzenbach wrote:
> Add support for offloading MQPRIO. The hardware has four priorities as well
> as four queues. Each queue must be a assigned with a unique priority.
>
> However, the priorities are only considered in TSN Tx mode. There are two
> TSN Tx modes. In case of MQPRIO the Qbv capability is not required.
> Therefore, use the legacy TSN Tx mode, which performs strict priority
> arbitration.
>
> Example for mqprio with hardware offload:
>
> |tc qdisc replace dev ${INTERFACE} handle 100 parent root mqprio num_tc 4 \
> | map 0 0 0 0 0 1 2 3 0 0 0 0 0 0 0 0 \
> | queues 1@0 1@1 1@2 1@3 \
> | hw 1
>
> The mqprio Qdisc also allows to configure the `preemptible_tcs'. However,
> frame preemption is not supported yet.
>
> Tested on Intel i225 and implemented by following data sheet section 7.5.2,
> Transmit Scheduling.
>
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
...
> diff --git a/drivers/net/ethernet/intel/igc/igc_defines.h b/drivers/net/ethernet/intel/igc/igc_defines.h
> index 5f92b3c7c3d4..73502a0b4df7 100644
> --- a/drivers/net/ethernet/intel/igc/igc_defines.h
> +++ b/drivers/net/ethernet/intel/igc/igc_defines.h
> @@ -547,6 +547,15 @@
>
> #define IGC_MAX_SR_QUEUES 2
>
> +#define IGC_TXARB_TXQ_PRIO_0_SHIFT 0
> +#define IGC_TXARB_TXQ_PRIO_1_SHIFT 2
> +#define IGC_TXARB_TXQ_PRIO_2_SHIFT 4
> +#define IGC_TXARB_TXQ_PRIO_3_SHIFT 6
> +#define IGC_TXARB_TXQ_PRIO_0_MASK GENMASK(1, 0)
> +#define IGC_TXARB_TXQ_PRIO_1_MASK GENMASK(3, 2)
> +#define IGC_TXARB_TXQ_PRIO_2_MASK GENMASK(5, 4)
> +#define IGC_TXARB_TXQ_PRIO_3_MASK GENMASK(7, 6)
> +
> /* Receive Checksum Control */
> #define IGC_RXCSUM_CRCOFL 0x00000800 /* CRC32 offload enable */
> #define IGC_RXCSUM_PCSD 0x00002000 /* packet checksum disabled */
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
...
> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
...
> @@ -106,7 +109,26 @@ 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.
> + */
> + txarb = rd32(IGC_TXARB);
> + txarb &= ~(IGC_TXARB_TXQ_PRIO_0_MASK |
> + IGC_TXARB_TXQ_PRIO_1_MASK |
> + IGC_TXARB_TXQ_PRIO_2_MASK |
> + IGC_TXARB_TXQ_PRIO_3_MASK);
> +
> + txarb |= 0x00 << IGC_TXARB_TXQ_PRIO_0_SHIFT;
> + txarb |= 0x01 << IGC_TXARB_TXQ_PRIO_1_SHIFT;
> + txarb |= 0x02 << IGC_TXARB_TXQ_PRIO_2_SHIFT;
> + txarb |= 0x03 << IGC_TXARB_TXQ_PRIO_3_SHIFT;
> + wr32(IGC_TXARB, txarb);
Hi Kurt,
It looks like the above would be a good candidate for using FIELD_PREP,
in which case the _SHIFT #defines can likely be removed.
Also, the logic above seems to be replicated in igc_tsn_enable_offload.
Perhaps a helper is appropriate.
> +
> adapter->flags &= ~IGC_FLAG_TSN_QBV_ENABLED;
> + adapter->flags &= ~IGC_FLAG_TSN_LEGACY_ENABLED;
>
> return 0;
> }
> @@ -123,6 +145,50 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
> wr32(IGC_DTXMXPKTSZ, IGC_DTXMXPKTSZ_TSN);
> wr32(IGC_TXPBS, IGC_TXPBSIZE_TSN);
>
> + if (adapter->strict_priority_enable) {
> + u32 txarb;
> + 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.
> + */
> + txarb = rd32(IGC_TXARB);
> + txarb &= ~(IGC_TXARB_TXQ_PRIO_0_MASK |
> + IGC_TXARB_TXQ_PRIO_1_MASK |
> + IGC_TXARB_TXQ_PRIO_2_MASK |
> + IGC_TXARB_TXQ_PRIO_3_MASK);
> + txarb |= adapter->queue_per_tc[3] << IGC_TXARB_TXQ_PRIO_0_SHIFT;
> + txarb |= adapter->queue_per_tc[2] << IGC_TXARB_TXQ_PRIO_1_SHIFT;
> + txarb |= adapter->queue_per_tc[1] << IGC_TXARB_TXQ_PRIO_2_SHIFT;
> + txarb |= adapter->queue_per_tc[0] << IGC_TXARB_TXQ_PRIO_3_SHIFT;
> + wr32(IGC_TXARB, txarb);
> +
> + /* 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++) {
> struct igc_ring *ring = adapter->tx_ring[i];
> u32 txqctl = 0;
...
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