Re: [PATCH net-next v4 2/2] net: stmmac: Tx coe sw fallback

[Serge Semin]

On Fri, Aug 18, 2023 at 09:53:50PM +0800, Rohan G Thomas wrote:
> Add sw fallback of tx checksum calculation for those tx queues that
> don't support tx checksum offloading. Because, some DWMAC IPs support
> tx checksum offloading only for a few initial tx queues, starting
> from tx queue 0.
> 
> Signed-off-by: Rohan G Thomas <rohan.g.thomas@xxxxxxxxx>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac.h  |  5 +++++
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 19 +++++++++++++++++++
>  .../ethernet/stmicro/stmmac/stmmac_platform.c |  4 ++++
>  include/linux/stmmac.h                        |  1 +
>  4 files changed, 29 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index 3401e888a9f6..64d7dbe474bd 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -210,12 +210,17 @@ struct stmmac_dma_conf {
>  	unsigned int dma_tx_size;
>  };
>  
> +#define STMMAC_PRIV_FLG_TXQ_COE_LIMIT	BIT(0)
> +
>  struct stmmac_priv {
>  	/* Frequently used values are kept adjacent for cache effect */
>  	u32 tx_coal_frames[MTL_MAX_TX_QUEUES];
>  	u32 tx_coal_timer[MTL_MAX_TX_QUEUES];
>  	u32 rx_coal_frames[MTL_MAX_TX_QUEUES];
>  

> +	u32 flags;

This looks redundant. See my last comment.

> +

> +	u32 tx_q_with_coe;

This one too. Can't you just use the
plat_stmmacenet_data.tx_queues_with_coe field?

>  	int hwts_tx_en;
>  	bool tx_path_in_lpi_mode;
>  	bool tso;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 733b5e900817..f9ab6635218c 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4409,6 +4409,17 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
>  	WARN_ON(tx_q->tx_skbuff[first_entry]);
>  
>  	csum_insertion = (skb->ip_summed == CHECKSUM_PARTIAL);
> +	/* Some DWMAC IPs support tx coe only for a few initial tx queues,
> +	 * starting from tx queue 0. So checksum offloading for those queues
> +	 * that don't support tx coe needs to fallback to software checksum
> +	 * calculation.
> +	 */

> +	if (csum_insertion && (priv->flags & STMMAC_PRIV_FLG_TXQ_COE_LIMIT) &&
> +	    queue >= priv->tx_q_with_coe) {
> +		if (unlikely(skb_checksum_help(skb)))
> +			goto dma_map_err;
> +		csum_insertion = !csum_insertion;
> +	}

just (csum_insertion && queue >= priv->plat->tx_queues_with_coe). See
further what to do for this to work as I suggested.

>  
>  	if (likely(priv->extend_desc))
>  		desc = (struct dma_desc *)(tx_q->dma_etx + entry);
> @@ -7401,6 +7412,14 @@ int stmmac_dvr_probe(struct device *device,
>  		dev_info(priv->device, "SPH feature enabled\n");
>  	}
>  

> +	if (priv->plat->tx_coe &&
> +	    priv->plat->tx_queues_with_coe < priv->plat->tx_queues_to_use) {
> +		priv->flags |= STMMAC_PRIV_FLG_TXQ_COE_LIMIT;
> +		priv->tx_q_with_coe = priv->plat->tx_queues_with_coe;
> +		dev_info(priv->device, "TX COE limited to %u tx queues\n",
> +			 priv->tx_q_with_coe);
> +	}

What about:
+	if (priv->plat->tx_coe && !priv->plat->tx_queues_with_coe)
+		priv->plat->tx_queues_with_coe = priv->plat->tx_queues_to_use;
+	else if (!priv->plat->tx_coe)
+		priv->plat->tx_queues_with_coe = 0;
+	else if (priv->plat->tx_queues_with_coe < priv->plat->tx_queues_to_use)
+		dev_info(priv->device, "TX COE is available for %u queues\n", priv->plat->tx_queues_with_coe);

?

-Serge(y)

> +
>  	/* Ideally our host DMA address width is the same as for the
>  	 * device. However, it may differ and then we have to use our
>  	 * host DMA width for allocation and the device DMA width for
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index be8e79c7aa34..0138b7c9c7ab 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -225,6 +225,10 @@ static int stmmac_mtl_setup(struct platform_device *pdev,
>  				 &plat->tx_queues_to_use))
>  		plat->tx_queues_to_use = 1;
>  
> +	if (of_property_read_u32(tx_node, "snps,tx-queues-with-coe",
> +				 &plat->tx_queues_with_coe))
> +		plat->tx_queues_with_coe = plat->tx_queues_to_use;
> +
>  	if (of_property_read_bool(tx_node, "snps,tx-sched-wrr"))
>  		plat->tx_sched_algorithm = MTL_TX_ALGORITHM_WRR;
>  	else if (of_property_read_bool(tx_node, "snps,tx-sched-wfq"))
> diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> index 784277d666eb..cb508164eaea 100644
> --- a/include/linux/stmmac.h
> +++ b/include/linux/stmmac.h
> @@ -252,6 +252,7 @@ struct plat_stmmacenet_data {
>  	u32 host_dma_width;
>  	u32 rx_queues_to_use;
>  	u32 tx_queues_to_use;
> +	u32 tx_queues_with_coe;
>  	u8 rx_sched_algorithm;
>  	u8 tx_sched_algorithm;
>  	struct stmmac_rxq_cfg rx_queues_cfg[MTL_MAX_RX_QUEUES];
> -- 
> 2.19.0
> 
>