6.15-stable review patch. If anyone has any objections, please let me know.
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From: Yao Zi ziyao@disroot.org
[ Upstream commit 4cc339ce482ba78589a2d5cbe1c84b735d263383 ]
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.
For backward compatibility with older devicetrees, probing won't fail if the APB clock isn't found. In this case, we emit a warning since the link will break if the speed changes.
Fixes: 33a1a01e3afa ("net: stmmac: Add glue layer for T-HEAD TH1520 SoC") Signed-off-by: Yao Zi ziyao@disroot.org Tested-by: Drew Fustini fustini@kernel.org Reviewed-by: Drew Fustini fustini@kernel.org Link: https://patch.msgid.link/20250808093655.48074-4-ziyao@disroot.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c index c72ee759aae5..f2946bea0bc2 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 +225,19 @@ static int thead_dwmac_probe(struct platform_device *pdev) return dev_err_probe(&pdev->dev, PTR_ERR(plat), "dt configuration failed\n");
+ /* + * The APB clock is essential for accessing glue registers. However, + * old devicetrees don't describe it correctly. We continue to probe + * and emit a warning if it isn't present. + */ + apb_clk = devm_clk_get_enabled(&pdev->dev, "apb"); + if (PTR_ERR(apb_clk) == -ENOENT) + dev_warn(&pdev->dev, + "cannot get apb clock, link may break after speed changes\n"); + else 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;