Re: [PATCH net 2/3] net: stmmac: thead: Get and enable APB clock on initialization

From: Drew Fustini <fustini@kernel.org>
To: Yao Zi <ziyao@disroot.org>
Cc: Guo Ren <guoren@kernel.org>, Fu Wei <wefu@redhat.com>,
	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>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alex@ghiti.fr>,
	Emil Renner Berthing <emil.renner.berthing@canonical.com>,
	Jisheng Zhang <jszhang@kernel.org>,
	linux-riscv@lists.infradead.org, netdev@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 2/3] net: stmmac: thead: Get and enable APB clock on initialization
Date: Tue, 29 Jul 2025 15:51:06 -0700	[thread overview]
Message-ID: <aIlQWmKY4Hhe/erO@x1> (raw)
In-Reply-To: <20250729093734.40132-3-ziyao@disroot.org>

On Tue, Jul 29, 2025 at 09:37:33AM +0000, Yao Zi wrote:
> It's necessary to adjust the MAC TX clock when the linkspeed changes,
> but it's noted such adjustment always fails on TH1520 SoC, and reading
> back from APB glue registers that control clock generation results in
> garbage, causing broken link.
> 
> With some testing, it's found a clock must be ungated for access to APB
> glue registers. Without any consumer, the clock is automatically
> disabled during late kernel startup. Let's get and enable it if it's
> described in devicetree.
> 
> Fixes: 33a1a01e3afa ("net: stmmac: Add glue layer for T-HEAD TH1520 SoC")
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
> index c72ee759aae5..95096244a846 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
> @@ -211,6 +211,7 @@ static int thead_dwmac_probe(struct platform_device *pdev)
>  	struct stmmac_resources stmmac_res;
>  	struct plat_stmmacenet_data *plat;
>  	struct thead_dwmac *dwmac;
> +	struct clk *apb_clk;
>  	void __iomem *apb;
>  	int ret;
>  
> @@ -224,6 +225,11 @@ static int thead_dwmac_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, PTR_ERR(plat),
>  				     "dt configuration failed\n");
>  
> +	apb_clk = devm_clk_get_optional_enabled(&pdev->dev, "apb");
> +	if (IS_ERR(apb_clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(apb_clk),
> +				     "failed to get apb clock\n");
> +
>  	dwmac = devm_kzalloc(&pdev->dev, sizeof(*dwmac), GFP_KERNEL);
>  	if (!dwmac)
>  		return -ENOMEM;
> -- 
> 2.50.1
> 

Thank you for tracking down root cause and fixing it.

Reviewed-by: Drew Fustini <fustini@kernel.org>

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