Subject: Re: [net-next v8 2/3] net: ethernet: mtk_eth_soc: Add RSS support

From: Jakub Kicinski <[email-masked]>
Date: Wed, 13 May 2026 18:56:25 -0700

On Sat,  9 May 2026 21:09:31 +0200 Frank Wunderlich wrote:
> From: Mason Chang <[email-masked]>
> 
> Add support for Receive Side Scaling.
> 
> We can adjust SMP affinity with the following command:
> echo [CPU bitmap num] > /proc/irq/[virtual IRQ ID]/smp_affinity,
> with interrupts evenly assigned to 4 CPUs, we were able to measure
> an RX throughput of 7.3Gbps using iperf3 on the MT7988. Further
> optimizations will be carried out in the future.

Would be great to split this up a little more for ease of review.

> +static int mtk_rss_init(struct mtk_eth *eth)
> +{
> +	const struct mtk_soc_data *soc = eth->soc;
> +	const struct mtk_reg_map *reg_map = eth->soc->reg_map;
> +	struct mtk_rss_params *rss_params = &eth->rss_params;

reverse xmas tree should be followed, please fix everywhere in this
submission 

> +	u32 val;
> +	int i;
> +
> +	netdev_rss_key_fill(rss_params->hash_key, MTK_RSS_HASH_KEYSIZE);
> +
> +	for (i = 0; i < MTK_RSS_MAX_INDIRECTION_TABLE; i++)
> +		rss_params->indirection_table[i] = ethtool_rxfh_indir_default(i, eth->soc->rss_num);
> +
> +	if (soc->rx.desc_size == sizeof(struct mtk_rx_dma)) {
> +		/* Set RSS rings to PSE modes */
> +		for (i = 1; i <= MTK_HW_LRO_RING_NUM(eth); i++) {
> +			val = mtk_r32(eth, MTK_LRO_CTRL_DW2_CFG(reg_map, i));
> +			val |= MTK_RING_PSE_MODE;
> +			mtk_w32(eth, val, MTK_LRO_CTRL_DW2_CFG(reg_map, i));
> +		}
> +
> +		/* Enable non-lro multiple rx */
> +		val = mtk_r32(eth, reg_map->pdma.lro_ctrl_dw0);
> +		val |= MTK_NON_LRO_MULTI_EN;
> +		mtk_w32(eth, val, reg_map->pdma.lro_ctrl_dw0);
> +
> +		/* Enable RSS dly int supoort */
> +		val |= MTK_LRO_DLY_INT_EN;
> +		mtk_w32(eth, val, reg_map->pdma.lro_ctrl_dw0);
> +	}
> +
> +	/* Hash Type */
> +	val = mtk_r32(eth, reg_map->pdma.rss_glo_cfg);
> +	val |= MTK_RSS_IPV4_STATIC_HASH;
> +	val |= MTK_RSS_IPV6_STATIC_HASH;
> +	mtk_w32(eth, val, reg_map->pdma.rss_glo_cfg);
> +
> +	/* Hash Key */
> +	for (i = 0; i < MTK_RSS_HASH_KEYSIZE / sizeof(u32); i++)
> +		mtk_w32(eth, rss_params->hash_key[i], MTK_RSS_HASH_KEY_DW(reg_map, i));
> +
> +	/* Select the size of indirection table */
> +	for (i = 0; i < MTK_RSS_MAX_INDIRECTION_TABLE / 16; i++)
> +		mtk_w32(eth, mtk_rss_indr_table(rss_params, i),
> +			MTK_RSS_INDR_TABLE_DW(reg_map, i));
> +
> +	/* Pause */
> +	val |= MTK_RSS_CFG_REQ;
> +	mtk_w32(eth, val, reg_map->pdma.rss_glo_cfg);
> +
> +	/* Enable RSS */
> +	val |= MTK_RSS_EN;
> +	mtk_w32(eth, val, reg_map->pdma.rss_glo_cfg);
> +
> +	/* Release pause */
> +	val &= ~(MTK_RSS_CFG_REQ);
> +	mtk_w32(eth, val, reg_map->pdma.rss_glo_cfg);
> +
> +	/* Set perRSS GRP INT */
> +	mtk_m32(eth, MTK_RX_DONE_INT(eth, MTK_RSS_RING(1)),
> +		MTK_RX_DONE_INT(eth, MTK_RSS_RING(1)), reg_map->pdma.int_grp);
> +	mtk_m32(eth, MTK_RX_DONE_INT(eth, MTK_RSS_RING(2)),
> +		MTK_RX_DONE_INT(eth, MTK_RSS_RING(2)), reg_map->pdma.int_grp + 0x4);
> +	mtk_m32(eth, MTK_RX_DONE_INT(eth, MTK_RSS_RING(3)),
> +		MTK_RX_DONE_INT(eth, MTK_RSS_RING(3)), reg_map->pdma.int_grp3);
> +
> +	return 0;
> +}

> +/* struct mtk_rss_params -	This is the structure holding parameters
> + *				for the RSS ring
> + * @hash_key			The element is used to record the
> + *				secret key for the RSS ring
> + * indirection_table		The element is used to record the
> + *				indirection table for the RSS ring
> + */

Quite odd looking comment. Having the right side aligned like that
makes it header to correlate where doc for fields start.
And there's @ missing for indirection_table.