Re: [RFC PATCH net-next v3 13/20] net: dsa: qca8k: make rgmii delay configurable

On Thu, May 06, 2021 at 02:10:33PM +0300, Vladimir Oltean wrote:

On Wed, May 05, 2021 at 12:29:07AM +0200, Ansuel Smith wrote:

quoted

The legacy qsdk code used a different delay instead of the max value.
Qsdk use 1 ps for rx and 2 ps for tx. Make these values configurable
using the standard rx/tx-internal-delay-ps ethernet binding and apply
qsdk values by default. The connected gmac doesn't add any delay so no
additional delay is added to tx/rx.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/net/dsa/qca8k.c | 51 +++++++++++++++++++++++++++++++++++++++--
 drivers/net/dsa/qca8k.h | 11 +++++----
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index 22334d416f53..cb9b44769e92 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c

@@ -779,6 +779,47 @@ qca8k_setup_mdio_bus(struct qca8k_priv *priv)
 	return 0;
 }
 
+static int
+qca8k_setup_of_rgmii_delay(struct qca8k_priv *priv)
+{
+	struct device_node *ports, *port;
+	u32 val;
+
+	ports = of_get_child_by_name(priv->dev->of_node, "ports");

Consider falling back to searching for the "ethernet-ports" name too,
DSA should now support both.

The function qca8k_setup_mdio_bus also checks for ports node. Should I
also there the fallback correct?

quoted

+	if (!ports)
+		return -EINVAL;
+
+	/* Assume only one port with rgmii-id mode */
+	for_each_available_child_of_node(ports, port) {
+		if (!of_property_match_string(port, "phy-mode", "rgmii-id"))
+			continue;
+
+		if (of_property_read_u32(port, "rx-internal-delay-ps", &val))
+			val = 2;
+
+		if (val > QCA8K_MAX_DELAY) {
+			dev_err(priv->dev, "rgmii rx delay is limited to more than 3ps, setting to the max value");
+			priv->rgmii_rx_delay = 3;

?!
3 picoseconds is not a lot of clock skew for a 125/25/2.5 MHz clock. 3 nanoseconds maybe?

quoted

+		} else {
+			priv->rgmii_rx_delay = val;
+		}
+
+		if (of_property_read_u32(port, "rx-internal-delay-ps", &val))
+			val = 1;
+
+		if (val > QCA8K_MAX_DELAY) {
+			dev_err(priv->dev, "rgmii tx delay is limited to more than 3ps, setting to the max value");
+			priv->rgmii_tx_delay = 3;
+		} else {
+			priv->rgmii_rx_delay = val;
+		}
+	}
+
+	of_node_put(ports);
+
+	return 0;
+}
+
 static int
 qca8k_setup(struct dsa_switch *ds)
 {

@@ -808,6 +849,10 @@ qca8k_setup(struct dsa_switch *ds)
 	if (ret)
 		return ret;
 
+	ret = qca8k_setup_of_rgmii_delay(priv);
+	if (ret)
+		return ret;
+
 	/* Enable CPU Port */
 	ret = qca8k_reg_set(priv, QCA8K_REG_GLOBAL_FW_CTRL0,
 			    QCA8K_GLOBAL_FW_CTRL0_CPU_PORT_EN);

@@ -1018,8 +1063,10 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
 		 */
 		qca8k_write(priv, reg,
 			    QCA8K_PORT_PAD_RGMII_EN |
-			    QCA8K_PORT_PAD_RGMII_TX_DELAY(QCA8K_MAX_DELAY) |
-			    QCA8K_PORT_PAD_RGMII_RX_DELAY(QCA8K_MAX_DELAY));
+			    QCA8K_PORT_PAD_RGMII_TX_DELAY(priv->rgmii_tx_delay) |
+			    QCA8K_PORT_PAD_RGMII_RX_DELAY(priv->rgmii_rx_delay) |
+			    QCA8K_PORT_PAD_RGMII_TX_DELAY_EN |
+			    QCA8K_PORT_PAD_RGMII_RX_DELAY_EN);
 		/* QCA8337 requires to set rgmii rx delay */
 		if (data->id == QCA8K_ID_QCA8337)
 			qca8k_write(priv, QCA8K_REG_PORT5_PAD_CTRL,

diff --git a/drivers/net/dsa/qca8k.h b/drivers/net/dsa/qca8k.h
index 0b503f78bf92..80830bb42736 100644
--- a/drivers/net/dsa/qca8k.h
+++ b/drivers/net/dsa/qca8k.h

@@ -36,12 +36,11 @@
 #define QCA8K_REG_PORT5_PAD_CTRL			0x008
 #define QCA8K_REG_PORT6_PAD_CTRL			0x00c
 #define   QCA8K_PORT_PAD_RGMII_EN			BIT(26)
-#define   QCA8K_PORT_PAD_RGMII_TX_DELAY(x)		\
-						((0x8 + (x & 0x3)) << 22)
-#define   QCA8K_PORT_PAD_RGMII_RX_DELAY(x)		\
-						((0x10 + (x & 0x3)) << 20)
-#define   QCA8K_MAX_DELAY				3
+#define   QCA8K_PORT_PAD_RGMII_TX_DELAY(x)		((x) << 22)
+#define   QCA8K_PORT_PAD_RGMII_RX_DELAY(x)		((x) << 20)
+#define	  QCA8K_PORT_PAD_RGMII_TX_DELAY_EN		BIT(25)
 #define   QCA8K_PORT_PAD_RGMII_RX_DELAY_EN		BIT(24)
+#define   QCA8K_MAX_DELAY				3
 #define   QCA8K_PORT_PAD_SGMII_EN			BIT(7)
 #define QCA8K_REG_PWS					0x010
 #define   QCA8K_PWS_SERDES_AEN_DIS			BIT(7)

@@ -251,6 +250,8 @@ struct qca8k_match_data {
 
 struct qca8k_priv {
 	u8 switch_revision;
+	u8 rgmii_tx_delay;
+	u8 rgmii_rx_delay;
 	struct regmap *regmap;
 	struct mii_bus *bus;
 	struct ar8xxx_port_status port_sts[QCA8K_NUM_PORTS];

-- 
2.30.2