netdev - Re: [PATCH net v2 1/3] net: stmmac: Limit the number of MTL queues to hardware capability

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Message-ID: <20250121142520.0000702e@gmail.com>
Date: Tue, 21 Jan 2025 14:25:20 +0800
From: Furong Xu <0x1207@...il.com>
To: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
 <joabreu@...opsys.com>, 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>, Maxime
 Coquelin <mcoquelin.stm32@...il.com>, Joao Pinto <Joao.Pinto@...opsys.com>,
 Vince Bridgers <vbridger@...nsource.altera.com>, netdev@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2 1/3] net: stmmac: Limit the number of MTL queues
 to hardware capability

On Tue, 21 Jan 2025 13:41:36 +0900, Kunihiko Hayashi <hayashi.kunihiko@...ionext.com> wrote:

> The number of MTL queues to use is specified by the parameter
> "snps,{tx,rx}-queues-to-use" from stmmac_platform layer.
> 
> However, the maximum numbers of queues are constrained by upper limits
> determined by the capability of each hardware feature. It's appropriate
> to limit the values not to exceed the upper limit values and display
> a warning message.
> 
> Fixes: d976a525c371 ("net: stmmac: multiple queues dt configuration")
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 7bf275f127c9..251a8c15637f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -7232,6 +7232,19 @@ static int stmmac_hw_init(struct stmmac_priv *priv)
>  	if (priv->dma_cap.tsoen)
>  		dev_info(priv->device, "TSO supported\n");
>  
> +	if (priv->plat->rx_queues_to_use > priv->dma_cap.number_rx_queues) {
> +		dev_warn(priv->device,
> +			 "Number of Rx queues exceeds dma capability (%d)\n",
> +			 priv->plat->rx_queues_to_use);
> +		priv->plat->rx_queues_to_use = priv->dma_cap.number_rx_queues;
> +	}
> +	if (priv->plat->tx_queues_to_use > priv->dma_cap.number_tx_queues) {
> +		dev_warn(priv->device,
> +			 "Number of Tx queues exceeds dma capability (%d)\n",
> +			 priv->plat->tx_queues_to_use);

I would prefer print these warnings like this:

dev_warn(priv->device, "Number of Tx queues (%u) exceeds dma capability (%u)\n",
priv->plat->tx_queues_to_use, priv->dma_cap.number_tx_queues);

And number_tx_queues, number_rx_queues are u32, so %u would be better.

This print format change is quite minor. Probably not worth a re-roll since one
can always view DMA capabilities by reading a debugfs entry.