[PATCH net v1 2/2] net: stmmac: eic7700: fix delay step calculation and ensure safe register initialization

[lizhi2@eswincomputing.com]

From: Zhi Li <lizhi2@eswincomputing.com>

Fix several issues in the EIC7700 DWMAC glue driver related to delay
configuration and register initialization.

The hardware implements TX/RX delay with a granularity of 20 ps per
step, but the driver previously assumed a 100 ps step. Update the
definitions to match the actual hardware behaviour and align with
the binding constraints.

Introduce explicit definitions for the maximum programmable delay
range based on the hardware limits.

Move HSP CSR configuration into the initialization path after clocks
are enabled. This ensures that all register accesses occur with the
required clocks active, avoiding undefined behaviour.

Clear the TXD and RXD delay control registers during initialization
to override any residual configuration left by the bootloader. This
ensures deterministic RGMII timing and prevents unintended delay
being applied.

The MAC RGMII delay programming is only required for 100Mbps and
1000Mbps modes, where precise clock-to-data alignment is necessary for
reliable sampling.

For 10Mbps operation, timing margins are sufficiently relaxed and no
additional delay compensation is required. In this case, the driver
falls back to a safe default configuration with delay disabled.

For unsupported or unexpected link speeds, the driver avoids
programming invalid delay values and falls back to a safe default
state by explicitly clearing the delay configuration.

Explicitly programming zero ensures that no residual delay settings
from previous configurations or bootloader state remain active.

These changes fix incorrect delay programming and initialization
ordering for existing users.

This also aligns the driver implementation with the updated device
tree binding.

Fixes: ea77dbbdbc4e ("net: stmmac: add Eswin EIC7700 glue driver")
Signed-off-by: Zhi Li <lizhi2@eswincomputing.com>
---
 .../ethernet/stmicro/stmmac/dwmac-eic7700.c   | 154 +++++++++++++-----
 1 file changed, 112 insertions(+), 42 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
index bcb8e000e720..0f1c62062797 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-eic7700.c
@@ -28,20 +28,31 @@
 
 /*
  * TX/RX Clock Delay Bit Masks:
- * - TX Delay: bits [14:8] — TX_CLK delay (unit: 0.1ns per bit)
- * - RX Delay: bits [30:24] — RX_CLK delay (unit: 0.1ns per bit)
+ * - TX Delay: bits [14:8] — TX_CLK delay (unit: 0.02ns per bit)
+ * - RX Delay: bits [30:24] — RX_CLK delay (unit: 0.02ns per bit)
  */
 #define EIC7700_ETH_TX_ADJ_DELAY	GENMASK(14, 8)
 #define EIC7700_ETH_RX_ADJ_DELAY	GENMASK(30, 24)
 
-#define EIC7700_MAX_DELAY_UNIT 0x7F
+#define EIC7700_MAX_DELAY_STEPS		0x7F
+#define EIC7700_DELAY_STEP_PS		20
+#define EIC7700_MAX_DELAY_PS	\
+	(EIC7700_MAX_DELAY_STEPS * EIC7700_DELAY_STEP_PS)
 
 static const char * const eic7700_clk_names[] = {
 	"tx", "axi", "cfg",
 };
 
 struct eic7700_qos_priv {
+	struct device *dev;
 	struct plat_stmmacenet_data *plat_dat;
+	struct regmap *eic7700_hsp_regmap;
+	u32 eth_axi_lp_ctrl_offset;
+	u32 eth_phy_ctrl_offset;
+	u32 eth_txd_offset;
+	u32 eth_clk_offset;
+	u32 eth_rxd_offset;
+	u32 eth_clk_dly_param;
 };
 
 static int eic7700_clks_config(void *priv, bool enabled)
@@ -61,8 +72,28 @@ static int eic7700_clks_config(void *priv, bool enabled)
 static int eic7700_dwmac_init(struct device *dev, void *priv)
 {
 	struct eic7700_qos_priv *dwc = priv;
+	int ret;
+
+	ret = eic7700_clks_config(dwc, true);
+	if (ret)
+		return ret;
+
+	ret = regmap_set_bits(dwc->eic7700_hsp_regmap,
+			      dwc->eth_phy_ctrl_offset,
+			      EIC7700_ETH_TX_CLK_SEL |
+			      EIC7700_ETH_PHY_INTF_SELI);
+	if (ret) {
+		eic7700_clks_config(dwc, false);
+		return ret;
+	}
+
+	regmap_write(dwc->eic7700_hsp_regmap, dwc->eth_axi_lp_ctrl_offset,
+		     EIC7700_ETH_CSYSREQ_VAL);
+
+	regmap_write(dwc->eic7700_hsp_regmap, dwc->eth_txd_offset, 0);
+	regmap_write(dwc->eic7700_hsp_regmap, dwc->eth_rxd_offset, 0);
 
-	return eic7700_clks_config(dwc, true);
+	return 0;
 }
 
 static void eic7700_dwmac_exit(struct device *dev, void *priv)
@@ -88,18 +119,38 @@ static int eic7700_dwmac_resume(struct device *dev, void *priv)
 	return ret;
 }
 
+static void eic7700_dwmac_fix_speed(void *priv, phy_interface_t interface,
+				    int speed, unsigned int mode)
+{
+	struct eic7700_qos_priv *dwc = (struct eic7700_qos_priv *)priv;
+	bool needs_calibration = false;
+
+	switch (speed) {
+	case SPEED_1000:
+	case SPEED_100:
+		needs_calibration = true;
+		fallthrough;
+	case SPEED_10:
+		break;
+	default:
+		dev_err(dwc->dev, "invalid speed %u\n", speed);
+		break;
+	}
+
+	if (needs_calibration) {
+		regmap_write(dwc->eic7700_hsp_regmap, dwc->eth_clk_offset,
+			     dwc->eth_clk_dly_param);
+	} else {
+		regmap_write(dwc->eic7700_hsp_regmap, dwc->eth_clk_offset, 0);
+	}
+}
+
 static int eic7700_dwmac_probe(struct platform_device *pdev)
 {
 	struct plat_stmmacenet_data *plat_dat;
 	struct stmmac_resources stmmac_res;
 	struct eic7700_qos_priv *dwc_priv;
-	struct regmap *eic7700_hsp_regmap;
-	u32 eth_axi_lp_ctrl_offset;
-	u32 eth_phy_ctrl_offset;
-	u32 eth_phy_ctrl_regset;
-	u32 eth_rxd_dly_offset;
-	u32 eth_dly_param = 0;
-	u32 delay_ps;
+	u32 delay_ps, val;
 	int i, ret;
 
 	ret = stmmac_get_platform_resources(pdev, &stmmac_res);
@@ -116,70 +167,88 @@ static int eic7700_dwmac_probe(struct platform_device *pdev)
 	if (!dwc_priv)
 		return -ENOMEM;
 
+	dwc_priv->dev = &pdev->dev;
+
 	/* Read rx-internal-delay-ps and update rx_clk delay */
 	if (!of_property_read_u32(pdev->dev.of_node,
 				  "rx-internal-delay-ps", &delay_ps)) {
-		u32 val = min(delay_ps / 100, EIC7700_MAX_DELAY_UNIT);
+		if (delay_ps % EIC7700_DELAY_STEP_PS)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+				"rx delay must be multiple of %dps\n",
+				EIC7700_DELAY_STEP_PS);
 
-		eth_dly_param &= ~EIC7700_ETH_RX_ADJ_DELAY;
-		eth_dly_param |= FIELD_PREP(EIC7700_ETH_RX_ADJ_DELAY, val);
-	} else {
-		return dev_err_probe(&pdev->dev, -EINVAL,
-			"missing required property rx-internal-delay-ps\n");
+		if (delay_ps > EIC7700_MAX_DELAY_PS)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+				"rx delay out of range\n");
+
+		val = delay_ps / EIC7700_DELAY_STEP_PS;
+
+		dwc_priv->eth_clk_dly_param &= ~EIC7700_ETH_RX_ADJ_DELAY;
+		dwc_priv->eth_clk_dly_param |=
+				 FIELD_PREP(EIC7700_ETH_RX_ADJ_DELAY, val);
 	}
 
 	/* Read tx-internal-delay-ps and update tx_clk delay */
 	if (!of_property_read_u32(pdev->dev.of_node,
 				  "tx-internal-delay-ps", &delay_ps)) {
-		u32 val = min(delay_ps / 100, EIC7700_MAX_DELAY_UNIT);
+		if (delay_ps % EIC7700_DELAY_STEP_PS)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+				"tx delay must be multiple of %dps\n",
+				EIC7700_DELAY_STEP_PS);
 
-		eth_dly_param &= ~EIC7700_ETH_TX_ADJ_DELAY;
-		eth_dly_param |= FIELD_PREP(EIC7700_ETH_TX_ADJ_DELAY, val);
-	} else {
-		return dev_err_probe(&pdev->dev, -EINVAL,
-			"missing required property tx-internal-delay-ps\n");
+		if (delay_ps > EIC7700_MAX_DELAY_PS)
+			return dev_err_probe(&pdev->dev, -EINVAL,
+				"tx delay out of range\n");
+
+		val = delay_ps / EIC7700_DELAY_STEP_PS;
+
+		dwc_priv->eth_clk_dly_param &= ~EIC7700_ETH_TX_ADJ_DELAY;
+		dwc_priv->eth_clk_dly_param |=
+				 FIELD_PREP(EIC7700_ETH_TX_ADJ_DELAY, val);
 	}
 
-	eic7700_hsp_regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
-							     "eswin,hsp-sp-csr");
-	if (IS_ERR(eic7700_hsp_regmap))
+	dwc_priv->eic7700_hsp_regmap =
+			syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+							"eswin,hsp-sp-csr");
+	if (IS_ERR(dwc_priv->eic7700_hsp_regmap))
 		return dev_err_probe(&pdev->dev,
-				PTR_ERR(eic7700_hsp_regmap),
+				PTR_ERR(dwc_priv->eic7700_hsp_regmap),
 				"Failed to get hsp-sp-csr regmap\n");
 
 	ret = of_property_read_u32_index(pdev->dev.of_node,
 					 "eswin,hsp-sp-csr",
-					 1, &eth_phy_ctrl_offset);
+					 1, &dwc_priv->eth_phy_ctrl_offset);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret,
 				     "can't get eth_phy_ctrl_offset\n");
 
-	regmap_read(eic7700_hsp_regmap, eth_phy_ctrl_offset,
-		    &eth_phy_ctrl_regset);
-	eth_phy_ctrl_regset |=
-		(EIC7700_ETH_TX_CLK_SEL | EIC7700_ETH_PHY_INTF_SELI);
-	regmap_write(eic7700_hsp_regmap, eth_phy_ctrl_offset,
-		     eth_phy_ctrl_regset);
-
 	ret = of_property_read_u32_index(pdev->dev.of_node,
 					 "eswin,hsp-sp-csr",
-					 2, &eth_axi_lp_ctrl_offset);
+					 2, &dwc_priv->eth_axi_lp_ctrl_offset);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret,
 				     "can't get eth_axi_lp_ctrl_offset\n");
 
-	regmap_write(eic7700_hsp_regmap, eth_axi_lp_ctrl_offset,
-		     EIC7700_ETH_CSYSREQ_VAL);
+	ret = of_property_read_u32_index(pdev->dev.of_node,
+					 "eswin,hsp-sp-csr",
+					 3, &dwc_priv->eth_clk_offset);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "can't get eth_clk_offset\n");
 
 	ret = of_property_read_u32_index(pdev->dev.of_node,
 					 "eswin,hsp-sp-csr",
-					 3, &eth_rxd_dly_offset);
+					 4, &dwc_priv->eth_txd_offset);
 	if (ret)
 		return dev_err_probe(&pdev->dev, ret,
-				     "can't get eth_rxd_dly_offset\n");
+				     "can't get eth_txd_offset\n");
 
-	regmap_write(eic7700_hsp_regmap, eth_rxd_dly_offset,
-		     eth_dly_param);
+	ret = of_property_read_u32_index(pdev->dev.of_node,
+					 "eswin,hsp-sp-csr",
+					 5, &dwc_priv->eth_rxd_offset);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "can't get eth_rxd_offset\n");
 
 	plat_dat->num_clks = ARRAY_SIZE(eic7700_clk_names);
 	plat_dat->clks = devm_kcalloc(&pdev->dev,
@@ -208,6 +277,7 @@ static int eic7700_dwmac_probe(struct platform_device *pdev)
 	plat_dat->exit = eic7700_dwmac_exit;
 	plat_dat->suspend = eic7700_dwmac_suspend;
 	plat_dat->resume = eic7700_dwmac_resume;
+	plat_dat->fix_mac_speed = eic7700_dwmac_fix_speed;
 
 	return devm_stmmac_pltfr_probe(pdev, plat_dat, &stmmac_res);
 }
-- 
2.25.1