linux-kernel - Re: [PATCH net v2] net: ethernet: ti: am65-cpsw: Fix multi queue Rx on J7

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Message-ID: <20241030191738.5bd12ccc@fedora.home>
Date: Wed, 30 Oct 2024 19:17:38 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Roger Quadros <rogerq@...nel.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard
 Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, Simon
 Horman <horms@...nel.org>, Vignesh Raghavendra <vigneshr@...com>, Siddharth
 Vadapalli <s-vadapalli@...com>, Md Danish Anwar <danishanwar@...com>,
 Govindarajan Sriramakrishnan <srk@...com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net v2] net: ethernet: ti: am65-cpsw: Fix multi queue Rx
 on J7

Hello Roger,

On Wed, 30 Oct 2024 15:53:58 +0200
Roger Quadros <rogerq@...nel.org> wrote:

> On J7 platforms, setting up multiple RX flows was failing
> as the RX free descriptor ring 0 is shared among all flows
> and we did not allocate enough elements in the RX free descriptor
> ring 0 to accommodate for all RX flows.
> 
> This issue is not present on AM62 as separate pair of
> rings are used for free and completion rings for each flow.
> 
> Fix this by allocating enough elements for RX free descriptor
> ring 0.
> 
> However, we can no longer rely on desc_idx (descriptor based
> offsets) to identify the pages in the respective flows as
> free descriptor ring includes elements for all flows.
> To solve this, introduce a new swdata data structure to store
> flow_id and page. This can be used to identify which flow (page_pool)
> and page the descriptor belonged to when popped out of the
> RX rings.

[...]

> @@ -339,7 +339,7 @@ static int am65_cpsw_nuss_rx_push(struct am65_cpsw_common *common,
>  	struct device *dev = common->dev;
>  	dma_addr_t desc_dma;
>  	dma_addr_t buf_dma;
> -	void *swdata;
> +	struct am65_cpsw_swdata *swdata;

There's a reverse xmas-tree issue here, where variables should be
declared from the longest line to the shortest.

[...]

>  static void am65_cpsw_nuss_rx_cleanup(void *data, dma_addr_t desc_dma)
>  {
> -	struct am65_cpsw_rx_flow *flow = data;
> +	struct am65_cpsw_rx_chn *rx_chn = data;
>  	struct cppi5_host_desc_t *desc_rx;
> -	struct am65_cpsw_rx_chn *rx_chn;
> +	struct am65_cpsw_swdata *swdata;
>  	dma_addr_t buf_dma;
>  	u32 buf_dma_len;
> -	void *page_addr;
> -	void **swdata;
> -	int desc_idx;
> +	struct page *page;
> +	u32 flow_id;

Here as well

[...]

>  	rx_chn->rx_chn = k3_udma_glue_request_rx_chn(dev, "rx", &rx_cfg);
> @@ -2455,10 +2441,12 @@ static int am65_cpsw_nuss_init_rx_chns(struct am65_cpsw_common *common)
>  		flow = &rx_chn->flows[i];
>  		flow->id = i;
>  		flow->common = common;
> +		flow->irq = -EINVAL;

I've tried to follow the code and I don't get that assignment for the
irq field, does it really have to do with the current change or is it
another issue that's being fixed ?

Sorry if I missed the point here.

Thanks,

Maxime