linux-kernel - Re: [PATCH net v4 3/3] net: stmmac: Specify hardware capability value when FIFO size isn't specified

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Message-ID: <d6265f8e-51bc-4556-9ecb-bfb73f86260d@arm.com>
Date: Fri, 31 Jan 2025 15:03:11 +0000
From: Steven Price <steven.price@....com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
 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>,
 Russell King <linux@...linux.org.uk>, 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 v4 3/3] net: stmmac: Specify hardware capability value
 when FIFO size isn't specified

On 31/01/2025 14:47, Andrew Lunn wrote:
>>> I'm guessing, but in your setup, i assume the value is never written
>>> to a register, hence 0 is O.K. e.g. dwmac1000_dma_operation_mode_rx(),
>>> the fifosz value is used to determine if flow control can be used, but
>>> is otherwise ignored.
>>
>> I haven't traced the code, but that fits my assumptions too.
> 
> I could probably figure it out using code review, but do you know
> which set of DMA operations your hardware uses? A quick look at
> dwmac-rk.c i see:
> 
>         /* If the stmmac is not already selected as gmac4,
>          * then make sure we fallback to gmac.
>          */
>         if (!plat_dat->has_gmac4)
>                 plat_dat->has_gmac = true;

has_gmac4 is false on this board, so has_gmac will be set to true here.

The DT compatible is rockchip,rk3288-gmac

Steve

> Which suggests there are two variants of the RockChip MAC.
> 
> 	Andrew