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

[Drew Fustini <fustini@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