[PATCH net-next v3 3/5] net: stmmac: sun55i: Make the delay step configurable

[Jerome Brunet]

The driver assumes a 100ps step for both TX and RX clock delays, which
does not match the A733 GMAC210.

Move the TX and RX delay steps to the match data and factor the delay
validation into a helper. The A523 keeps the 100ps step to preserve the DT
ABI, although the vendor reports actual steps of 180ps for TX and 530ps
for RX.

Signed-off-by: Jerome Brunet <jbrunet at baylibre.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-sun55i.c | 58 +++++++++++++++-------
 1 file changed, 39 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun55i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun55i.c
index c4df53285007..e759311f40fc 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun55i.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun55i.c
@@ -42,6 +42,8 @@ struct sun55i_gmac_data {
 	int (*init_resources)(struct platform_device *pdev,
 			      struct sun55i_gmac *gmac);
 	unsigned int flags;
+	u32 txdly_step_ps;
+	u32 rxdly_step_ps;
 	u32 offset;
 };
 
@@ -62,38 +64,47 @@ static int sun55i_gmac200_init_resources(struct platform_device *pdev,
 	return 0;
 }
 
+static int sun55i_gmac200_validate_delay(struct device *dev, const char *dir,
+					 u32 *val, u32 step, u32 max)
+{
+	if (*val % step)
+		return dev_err_probe(dev, -EINVAL,
+				     "%s-delay must be a multiple of %ups\n", dir, step);
+	max *= step;
+	if (*val > max)
+		return dev_err_probe(dev, -EINVAL,
+				     "%s clock delay exceeds maximum (%ups > %ups)\n",
+				     dir, *val, max);
+	*val /= step;
+	dev_dbg(dev, "set %s-delay to %x\n", dir, *val);
+
+	return 0;
+}
+
 static int sun55i_gmac200_setup(struct device *dev,
 				struct plat_stmmacenet_data *plat,
 				const struct sun55i_gmac *gmac)
 {
 	struct device_node *node = dev->of_node;
-	u32 val, reg = 0;
+	u32 val, step, max, reg = 0;
 	int ret;
 
 	if (!of_property_read_u32(node, "tx-internal-delay-ps", &val)) {
-		if (val % 100)
-			return dev_err_probe(dev, -EINVAL,
-					     "tx-delay must be a multiple of 100ps\n");
-		val /= 100;
-		dev_dbg(dev, "set tx-delay to %x\n", val);
-		if (!FIELD_FIT(SYSCON_ETXDC_MASK, val))
-			return dev_err_probe(dev, -EINVAL,
-					     "TX clock delay exceeds maximum (%u00ps > %lu00ps)\n",
-					     val, FIELD_MAX(SYSCON_ETXDC_MASK));
+		step = gmac->data->txdly_step_ps;
+		max = FIELD_MAX(SYSCON_ETXDC_MASK);
+		ret = sun55i_gmac200_validate_delay(dev, "tx", &val, step, max);
+		if (ret)
+			return ret;
 
 		reg |= FIELD_PREP(SYSCON_ETXDC_MASK, val);
 	}
 
 	if (!of_property_read_u32(node, "rx-internal-delay-ps", &val)) {
-		if (val % 100)
-			return dev_err_probe(dev, -EINVAL,
-					     "rx-delay must be a multiple of 100ps\n");
-		val /= 100;
-		dev_dbg(dev, "set rx-delay to %x\n", val);
-		if (!FIELD_FIT(SYSCON_ERXDC_MASK, val))
-			return dev_err_probe(dev, -EINVAL,
-					     "RX clock delay exceeds maximum (%u00ps > %lu00ps)\n",
-					     val, FIELD_MAX(SYSCON_ERXDC_MASK));
+		step = gmac->data->rxdly_step_ps;
+		max = FIELD_MAX(SYSCON_ERXDC_MASK);
+		ret = sun55i_gmac200_validate_delay(dev, "rx", &val, step, max);
+		if (ret)
+			return ret;
 
 		reg |= FIELD_PREP(SYSCON_ERXDC_MASK, val);
 	}
@@ -175,6 +186,15 @@ static const struct sun55i_gmac_data sun55i_a523_gmac200_data = {
 	.init_resources = sun55i_gmac200_init_resources,
 	.flags = STMMAC_FLAG_SPH_DISABLE,
 	.offset = 0x34,
+	/*
+	 * The actual delay steps reported by the manufacturer are:
+	 * - Tx: 180ps
+	 * - Rx: 530ps
+	 *
+	 * Correcting them would break the DT ABI of the published DTs.
+	 */
+	.txdly_step_ps = 100,
+	.rxdly_step_ps = 100,
 };
 
 static const struct of_device_id sun55i_gmac200_match[] = {

-- 
2.53.0