[RFC PATCH v2 4/7] net: stmmac: dwmac-meson8b: add support for the Amlogic T7

[Lucas Tanure]

The glue registers on the T7 are laid out exactly as the G12A ones, RX
delay field included, so the T7 can reuse the G12A settings.

What it does not share is how the controller reaches memory. That path
runs through a pipeline stage with a gate of its own, and no other
device has any use for that gate. Nothing claims it, so it is switched
off as unused and a transfer that has started can never finish.

Without that gate the controller cannot do DMA at all, so it is
required rather than optional: a clear probe failure beats an
undiagnosable hang later.

Assisted-by: LLM
Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>
Signed-off-by: Lucas Tanure <tanure at linux.com>
---
 .../ethernet/stmicro/stmmac/dwmac-meson8b.c   | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
index d73dfd0ac167..dd10d719ab84 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
@@ -81,6 +81,7 @@ struct meson8b_dwmac;
 struct meson8b_dwmac_data {
 	int (*set_phy_mode)(struct meson8b_dwmac *dwmac);
 	bool has_prg_eth1_rgmii_rx_delay;
+	bool has_pipeline_clk;
 };
 
 struct meson8b_dwmac {
@@ -402,6 +403,7 @@ static int meson8b_dwmac_probe(struct platform_device *pdev)
 	struct plat_stmmacenet_data *plat_dat;
 	struct stmmac_resources stmmac_res;
 	struct meson8b_dwmac *dwmac;
+	struct clk *pipeline_clk;
 	u32 tx_delay_ps;
 	int ret;
 
@@ -485,6 +487,13 @@ static int meson8b_dwmac_probe(struct platform_device *pdev)
 	if (IS_ERR(dwmac->timing_adj_clk))
 		return PTR_ERR(dwmac->timing_adj_clk);
 
+	if (dwmac->data->has_pipeline_clk) {
+		pipeline_clk = devm_clk_get_enabled(dwmac->dev, "pipeline");
+		if (IS_ERR(pipeline_clk))
+			return dev_err_probe(dwmac->dev, PTR_ERR(pipeline_clk),
+					     "missing pipeline clock\n");
+	}
+
 	ret = meson8b_init_rgmii_delays(dwmac);
 	if (ret)
 		return ret;
@@ -521,6 +530,12 @@ static const struct meson8b_dwmac_data meson_g12a_dwmac_data = {
 	.has_prg_eth1_rgmii_rx_delay = true,
 };
 
+static const struct meson8b_dwmac_data meson_t7_dwmac_data = {
+	.set_phy_mode = meson_axg_set_phy_mode,
+	.has_prg_eth1_rgmii_rx_delay = true,
+	.has_pipeline_clk = true,
+};
+
 static const struct of_device_id meson8b_dwmac_match[] = {
 	{
 		.compatible = "amlogic,meson8b-dwmac",
@@ -542,6 +557,10 @@ static const struct of_device_id meson8b_dwmac_match[] = {
 		.compatible = "amlogic,meson-g12a-dwmac",
 		.data = &meson_g12a_dwmac_data,
 	},
+	{
+		.compatible = "amlogic,t7-dwmac",
+		.data = &meson_t7_dwmac_data,
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, meson8b_dwmac_match);
-- 
2.56.0