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Message-ID: <b2cb86f7-c16a-44d2-a7b9-eb379784ff83@intel.com>
Date: Tue, 4 Jun 2024 15:25:41 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Frank Wunderlich <linux@...web.de>, Felix Fietkau <nbd@....name>, "Sean
Wang" <sean.wang@...iatek.com>, Mark Lee <Mark-MC.Lee@...iatek.com>, "Lorenzo
Bianconi" <lorenzo@...nel.org>, "David S. Miller" <davem@...emloft.net>,
"Eric Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
Abeni <pabeni@...hat.com>, Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
CC: Frank Wunderlich <frank-w@...lic-files.de>, John Crispin
<john@...ozen.org>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>,
<bc-bocun.chen@...iatek.com>, Daniel Golle <daniel@...rotopia.org>
Subject: Re: [net v3] net: ethernet: mtk_eth_soc: handle dma buffer size soc
specific
On 6/3/2024 12:25 PM, Frank Wunderlich wrote:
> @@ -1142,40 +1142,46 @@ static int mtk_init_fq_dma(struct mtk_eth *eth)
> cnt * soc->tx.desc_size,
> ð->phy_scratch_ring,
> GFP_KERNEL);
> +
> if (unlikely(!eth->scratch_ring))
> return -ENOMEM;
>
> - eth->scratch_head = kcalloc(cnt, MTK_QDMA_PAGE_SIZE, GFP_KERNEL);
> - if (unlikely(!eth->scratch_head))
> - return -ENOMEM;
> + phy_ring_tail = eth->phy_scratch_ring + soc->tx.desc_size * (cnt - 1);
>
> - dma_addr = dma_map_single(eth->dma_dev,
> - eth->scratch_head, cnt * MTK_QDMA_PAGE_SIZE,
> - DMA_FROM_DEVICE);
> - if (unlikely(dma_mapping_error(eth->dma_dev, dma_addr)))
> - return -ENOMEM;
> + for (j = 0; j < DIV_ROUND_UP(soc->tx.fq_dma_size, MTK_FQ_DMA_LENGTH); j++) {
> + len = min_t(int, cnt - j * MTK_FQ_DMA_LENGTH, MTK_FQ_DMA_LENGTH);
> + eth->scratch_head[j] = kcalloc(len, MTK_QDMA_PAGE_SIZE, GFP_KERNEL);
>
> - phy_ring_tail = eth->phy_scratch_ring + soc->tx.desc_size * (cnt - 1);
> + if (unlikely(!eth->scratch_head[j]))
> + return -ENOMEM;
>
> - for (i = 0; i < cnt; i++) {
> - dma_addr_t addr = dma_addr + i * MTK_QDMA_PAGE_SIZE;
> - struct mtk_tx_dma_v2 *txd;
> + dma_addr = dma_map_single(eth->dma_dev,
> + eth->scratch_head[j], len * MTK_QDMA_PAGE_SIZE,
> + DMA_FROM_DEVICE);
>
> - txd = eth->scratch_ring + i * soc->tx.desc_size;
> - txd->txd1 = addr;
> - if (i < cnt - 1)
> - txd->txd2 = eth->phy_scratch_ring +
> - (i + 1) * soc->tx.desc_size;
> + if (unlikely(dma_mapping_error(eth->dma_dev, dma_addr)))
> + return -ENOMEM;
>
> - txd->txd3 = TX_DMA_PLEN0(MTK_QDMA_PAGE_SIZE);
> - if (MTK_HAS_CAPS(soc->caps, MTK_36BIT_DMA))
> - txd->txd3 |= TX_DMA_PREP_ADDR64(addr);
> - txd->txd4 = 0;
> - if (mtk_is_netsys_v2_or_greater(eth)) {
> - txd->txd5 = 0;
> - txd->txd6 = 0;
> - txd->txd7 = 0;
> - txd->txd8 = 0;
> + for (i = 0; i < cnt; i++) {
> + struct mtk_tx_dma_v2 *txd;
> +
> + txd = eth->scratch_ring + (j * MTK_FQ_DMA_LENGTH + i) * soc->tx.desc_size;
> + txd->txd1 = dma_addr + i * MTK_QDMA_PAGE_SIZE;
> + if (j * MTK_FQ_DMA_LENGTH + i < cnt)
> + txd->txd2 = eth->phy_scratch_ring +
> + (j * MTK_FQ_DMA_LENGTH + i + 1) * soc->tx.desc_size;
> +
> + txd->txd3 = TX_DMA_PLEN0(MTK_QDMA_PAGE_SIZE);
> + if (MTK_HAS_CAPS(soc->caps, MTK_36BIT_DMA))
> + txd->txd3 |= TX_DMA_PREP_ADDR64(dma_addr + i * MTK_QDMA_PAGE_SIZE);
> +
> + txd->txd4 = 0;
> + if (mtk_is_netsys_v2_or_greater(eth)) {
> + txd->txd5 = 0;
> + txd->txd6 = 0;
> + txd->txd7 = 0;
> + txd->txd8 = 0;
> + }
This block of change was a bit hard to understand what was going on, but
I think I get the result is that you end up allocating different set of
scratch_head per size vs the original only having one scratch_head per
device?
Perhaps you can explain, but we're now allocating a bunch of different
scratch_head pointers.. However, in the patch, the only places that we
modify scratch_head appear to be the allocation path and the free path..
but I can't seem to understand how that would impact the users of
scratch head? I guess it changes the dma_addr which then changes the txd
values we program?
Ok.
I sort of understand whats going on here, but it was a fair bit to fully
grok this flow.
Overall, I'm no expert on the part or DMA here, but:
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
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