Re: [PATCH net v2 2/3] net: stmmac: thead: Get and enable APB clock on initialization

From: Drew Fustini <fustini@kernel.org>
To: Rob Herring <robh@kernel.org>
Cc: Yao Zi <ziyao@disroot.org>, 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>,
	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 v2 2/3] net: stmmac: thead: Get and enable APB clock on initialization
Date: Sun, 3 Aug 2025 11:46:05 -0700	[thread overview]
Message-ID: <aI-ubdx3FJj_wm3a@gen8> (raw)
In-Reply-To: <20250803170206.GA525144-robh@kernel.org>

On Sun, Aug 03, 2025 at 12:02:06PM -0500, Rob Herring wrote:
> On Fri, Aug 01, 2025 at 09:12:39AM +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>
> > Reviewed-by: Drew Fustini <fustini@kernel.org>
> > Tested-by: Drew Fustini <fustini@kernel.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");
> 
> The description sounds like this should not be optional. The binding 
> change also makes it not optional.

Good point, it should be devm_clk_get_enabled() otherwise the link speed
change bug will be possible. This series also changes the schema and dts
so I don't think compatibility is a problem.

Thanks,
Drew

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