linux-kernel - RE: [net v2] net: ethernet: mtk_eth_soc: handle dma buffer size soc specific

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Date: Mon, 27 May 2024 15:55:55 +0000
From: Sunil Kovvuri Goutham <sgoutham@...vell.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" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>,
        Daniel Golle <daniel@...rotopia.org>
Subject: RE: [net v2] net: ethernet: mtk_eth_soc: handle dma buffer size soc
 specific



> -----Original Message-----
> From: Frank Wunderlich <linux@...web.de>
> Sent: Monday, May 27, 2024 7:52 PM
> To: 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;
> Daniel Golle <daniel@...rotopia.org>
> Subject: [net v2] net: ethernet: mtk_eth_soc: handle dma buffer size soc specific
> 
> From: Frank Wunderlich <frank-w@...lic-files.de>
> 
> The mainline MTK ethernet driver suffers long time from rarly but annoying tx
> queue timeouts. We think that this is caused by fixed dma sizes hardcoded for
> all SoCs.
> 
> Use the dma-size implementation from SDK in a per SoC manner.
> 
> Fixes: 656e705243fd ("net-next: mediatek: add support for MT7623
> ethernet")
> Suggested-by: Daniel Golle <daniel@...rotopia.org>
> Signed-off-by: Frank Wunderlich <frank-w@...lic-files.de>

.............
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index cae46290a7ae..f1ff1be73926 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c

............
> @@ -1142,40 +1142,46 @@ static int mtk_init_fq_dma(struct mtk_eth *eth)
>  						       cnt * soc->tx.desc_size,
>  						       &eth->phy_scratch_ring,
>  						       GFP_KERNEL);

.............
> -	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);
> 

As per commit msg, the fix is for transmit queue timeouts.
But the DMA buffer changes seems for receive pkts.
Can you please elaborate the connection here.

Thanks,
Sunil.