linux-kernel - Re: [PATCH net] net: stmmac: thead: Enable TX clock before MAC initialization

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Message-ID: <aI/5aS064VKfLTJT@x1>
Date: Sun, 3 Aug 2025 17:06:01 -0700
From: Drew Fustini <fustini@...nel.org>
To: Yao Zi <ziyao@...root.org>
Cc: Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.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>,
	Emil Renner Berthing <emil.renner.berthing@...onical.com>,
	Jisheng Zhang <jszhang@...nel.org>, nux-riscv@...ts.infradead.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: stmmac: thead: Enable TX clock before MAC
 initialization

On Fri, Aug 01, 2025 at 09:45:07AM +0000, Yao Zi wrote:
> The clk_tx_i clock must be supplied to the MAC for successful
> initialization. On TH1520 SoC, the clock is provided by an internal
> divider configured through GMAC_PLLCLK_DIV register when using RGMII
> interface. However, currently we don't setup the divider before
> initialization of the MAC, resulting in DMA reset failures if the
> bootloader/firmware doesn't enable the divider,
> 
> [    7.839601] thead-dwmac ffe7060000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0
> [    7.938338] thead-dwmac ffe7060000.ethernet eth0: PHY [stmmac-0:02] driver [RTL8211F Gigabit Ethernet] (irq=POLL)
> [    8.160746] thead-dwmac ffe7060000.ethernet eth0: Failed to reset the dma
> [    8.170118] thead-dwmac ffe7060000.ethernet eth0: stmmac_hw_setup: DMA engine initialization failed
> [    8.179384] thead-dwmac ffe7060000.ethernet eth0: __stmmac_open: Hw setup failed
> 
> Let's simply write GMAC_PLLCLK_DIV_EN to GMAC_PLLCLK_DIV to enable the
> divider before MAC initialization. The rate doesn't matter, which we
> could reclock properly according to the link speed later after link is
> up.
> 
> Signed-off-by: Yao Zi <ziyao@...root.org>
> Fixes: 33a1a01e3afa ("net: stmmac: Add glue layer for T-HEAD TH1520 SoC")
> ---
> 
> Note that the DMA reset failures cannot be reproduced with the vendor
> U-Boot, which always enables the divider, regardless whether the port is
> used[1].

Thanks for sending this fix. I do now have a 16GB RAM LPi4a so I'll try
to get the mainline u-boot on there in order to test.

Thanks,
Drew