netdev - Re: [PATCH netdev] net: stmmac: dwmac-rk: Provide FIFO sizes for DWMAC 1000

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Message-ID: <ed89be56-b616-4a14-aab2-294fddd89dae@lunn.ch>
Date: Tue, 4 Feb 2025 20:45:50 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Chen-Yu Tsai <wens@...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>,
	Heiko Stuebner <heiko@...ech.de>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Steven Price <steven.price@....com>, Chen-Yu Tsai <wens@...e.org>,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	stable@...r.kernel.org
Subject: Re: [PATCH netdev] net: stmmac: dwmac-rk: Provide FIFO sizes for
 DWMAC 1000

On Wed, Feb 05, 2025 at 12:13:59AM +0800, Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@...e.org>
> 
> The DWMAC 1000 DMA capabilities register does not provide actual
> FIFO sizes, nor does the driver really care. If they are not
> provided via some other means, the driver will work fine, only
> disallowing changing the MTU setting.
> 
> The recent commit 8865d22656b4 ("net: stmmac: Specify hardware
> capability value when FIFO size isn't specified") changed this by
> requiring the FIFO sizes to be provided, breaking devices that were
> working just fine.
> 
> Provide the FIFO sizes through the driver's platform data, to not
> only fix the breakage, but also enable MTU changes. The FIFO sizes
> are confirmed to be the same across RK3288, RK3328, RK3399 and PX30,
> based on their respective manuals. It is likely that Rockchip
> synthesized their DWMAC 1000 with the same parameters on all their
> chips that have it.
> 
> Fixes: eaf4fac47807 ("net: stmmac: Do not accept invalid MTU values")
> Fixes: 8865d22656b4 ("net: stmmac: Specify hardware capability value when FIFO size isn't specified")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> ---
> The reason for stable inclusion is not to fix the device breakage
> (which only broke in v6.14-rc1), but to provide the values so that MTU
> changes can work in older kernels.

Allowing the MTU to be changed is probably classed as a new feature,
not bug fix.

I _think_ this also allows flow control, which again is a new feature.

Please submit to net-next.

	Andrew