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

From: Steven Price <steven.price@arm.com>
To: Chen-Yu Tsai <wens@kernel.org>,
	Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Heiko Stuebner <heiko@sntech.de>
Cc: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
	Chen-Yu Tsai <wens@csie.org>,
	Kunihiko Hayashi <hayashi.kunihiko@socionext.com>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
	stable@vger.kernel.org
Subject: Re: [PATCH netdev] net: stmmac: dwmac-rk: Provide FIFO sizes for DWMAC 1000
Date: Thu, 6 Feb 2025 09:35:03 +0000	[thread overview]
Message-ID: <de9aa254-dcfc-4a7d-b89d-79b41649a6b2@arm.com> (raw)
In-Reply-To: <20250204161359.3335241-1-wens@kernel.org>

On 04/02/2025 16:13, Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@csie.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@vger.kernel.org>
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>

I think it's better at this stage to apply the revert first. However
I've run this on my board (Firefly RK3288) and it works, so when rebased
onto the (reverted) revert:

Tested-by: Steven Price <steven.price@arm.com>

Thanks,
Steve

> ---
> 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.
> 
> Since a fix for stmmac in general has already been sent [1] and a revert
> was also proposed [2], I'll refrain from sending mine.
> 
> [1] https://lore.kernel.org/all/20250203093419.25804-1-steven.price@arm.com/
> [2] https://lore.kernel.org/all/Z6Clkh44QgdNJu_O@shell.armlinux.org.uk/
> 
>  drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> index a4dc89e23a68..71a4c4967467 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> @@ -1966,8 +1966,11 @@ static int rk_gmac_probe(struct platform_device *pdev)
>  	/* If the stmmac is not already selected as gmac4,
>  	 * then make sure we fallback to gmac.
>  	 */
> -	if (!plat_dat->has_gmac4)
> +	if (!plat_dat->has_gmac4) {
>  		plat_dat->has_gmac = true;
> +		plat_dat->rx_fifo_size = 4096;
> +		plat_dat->tx_fifo_size = 2048;
> +	}
>  	plat_dat->fix_mac_speed = rk_fix_speed;
>  
>  	plat_dat->bsp_priv = rk_gmac_setup(pdev, plat_dat, data);

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