linux-kernel - Re: [PATCH net v3 1/3] net: stmmac: Limit the number of MTL queues to hardware capability

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Message-ID: <bc3734ba-e68d-4700-8596-2710f6101f8f@socionext.com>
Date: Mon, 27 Jan 2025 10:18:38 +0900
From: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
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>,
 Yanteng Si <si.yanteng@...ux.dev>, Furong Xu <0x1207@...il.com>,
 Joao Pinto <Joao.Pinto@...opsys.com>, netdev@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3 1/3] net: stmmac: Limit the number of MTL queues to
 hardware capability

On 2025/01/24 20:43, Russell King (Oracle) wrote:
> On Fri, Jan 24, 2025 at 07:13:57PM +0900, Kunihiko Hayashi 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.
>>
>> This only works if the hardware capability has the upper limit values.
>>
>> 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 | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 7bf275f127c9..be1e6fa6d557 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -7232,6 +7232,21 @@ static int stmmac_hw_init(struct stmmac_priv
> *priv)
>>   	if (priv->dma_cap.tsoen)
>>   		dev_info(priv->device, "TSO supported\n");
>>   
>> +	if (priv->dma_cap.number_rx_queues &&
>> +	    priv->dma_cap.number_rx_queues < priv->plat->rx_queues_to_use)
> {
> 
> While this looks "nicer", which of these two do you think reads better
> and is easier to understand:
> 
> "If priv->dma_cap.number_rx_queues is set, and
>   priv->dma_cap.number_rx_queues is less than
>   priv->plat->rx_queues_to_use then print a message about
>   priv->plat->rx_queues_to_use exceeding priv->dma_cap.number_rx_queues"
> 
> "If priv->dma_cap.number_rx_queues is set, and
>   priv->plat->rx_queues_to_use is greater than
>   priv->dma_cap.number_rx_queues, then print a message about
>   priv->plat->rx_queues_to_use exceeding priv->dma_cap.number_rx_queues"
> 
> With the former one has to mentally flip the test around in the if
> statement to check that it does indeed match the warning that is
> printed.

This patch focuses only on the conditional lines, however, certainly
it's not good to have the meaning of the message and the condition
reversed.

I'll fix it next.

Thank you,

---
Best Regards
Kunihiko Hayashi