[PATCH] net: phy: dp83867: default to 2ns delay if unspecified in device-tree

[Siddharth Vadapalli]

Since Linux commit c360eb0c3ccb ("dt-bindings: net: ethernet-controller:
Add informative text about RGMII delays"), the interpretation of RGMII
delays has changed. Prior to the commit, the RGMII Variant among "rgmii",
"rgmii-id", "rgmii-rxid" and "rgmii-txid" clearly specified whether it is
the MAC or the PHY that "should" add the delay. However, post that commit,
the RGMII Variant only specifies whether or not there is a delay on the
PCB traces between the MAC and the PHY, leaving it open as to who adds the
delay.

Hence, instead of enforcing the existence of the device-tree properties
"ti,rx-internal-delay" and "ti,tx-internal-delay", default to a delay
of 2ns, while continuing to override this delay with the aforementioned
properties, if they exist in the device-tree.

This is in line with the Linux driver implementation updated by commit
6bf78849371d ("net: phy: dp83867: use 2ns delay if not specified in DTB").

Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
---

Hello,

This patch is based on commit
47e064f1317 Merge branch 'master' of https://source.denx.de/u-boot/custodians/u-boot-sh
of the master branch of U-Boot.

This patch fixes Ethernet issues on AM62D2-EVM with the DP83867 Ethernet PHY.
Although all platforms using the DP83867 Ethernet PHY have switched from "rgmii-rxid"
to "rgmii-id" in the device-tree, they haven't faced any issues due to the
"ti,rx-internal-delay" property being retained. For AM62D2 however, the device-tree
had "rgmii-id" specified as the phy-mode from the start, as a result of which, the
delay was never specified. This issue has been handled in Linux by an update to the DP83867
driver as mentioned in the commit message above. A similar update is required for U-Boot as
well, which is being implemented by this patch.

Patch has been tested on AM62D2-EVM (using 'rgmii-id' and doesn't have the delay property)
and on J7200-EVM (using 'rgmii-id' but has the delay property).
AM62D2 Logs:
https://gist.github.com/Siddharth-Vadapalli-at-TI/230497066b1f746e074ea230e9d10fdd
J7200 Logs:
https://gist.github.com/Siddharth-Vadapalli-at-TI/bc55607aedffa9a51df4e3557298ff92

Regards,
Siddharth.

 drivers/net/phy/dp83867.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/net/phy/dp83867.c b/drivers/net/phy/dp83867.c
index 772cde1c520..0f0b5352eef 100644
--- a/drivers/net/phy/dp83867.c
+++ b/drivers/net/phy/dp83867.c
@@ -203,32 +203,24 @@ static int dp83867_of_init(struct phy_device *phydev)
 				"Should be 'rgmii-id' to use internal delays\n");
 	}
 
-	/* RX delay *must* be specified if internal delay of RX is used. */
+	dp83867->rx_id_delay = DP83867_RGMIIDCTL_2_00_NS;
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
 	    phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID) {
 		ret = ofnode_read_u32(node, "ti,rx-internal-delay",
 				      &dp83867->rx_id_delay);
-		if (ret) {
-			pr_debug("ti,rx-internal-delay must be specified\n");
-			return ret;
-		}
-		if (dp83867->rx_id_delay > DP83867_RGMII_RX_CLK_DELAY_MAX) {
+		if (!ret && dp83867->rx_id_delay > DP83867_RGMII_RX_CLK_DELAY_MAX) {
 			pr_debug("ti,rx-internal-delay value of %u out of range\n",
 				 dp83867->rx_id_delay);
 			return -EINVAL;
 		}
 	}
 
-	/* TX delay *must* be specified if internal delay of RX is used. */
+	dp83867->tx_id_delay = DP83867_RGMIIDCTL_2_00_NS;
 	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
 	    phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID) {
 		ret = ofnode_read_u32(node, "ti,tx-internal-delay",
 				      &dp83867->tx_id_delay);
-		if (ret) {
-			debug("ti,tx-internal-delay must be specified\n");
-			return ret;
-		}
-		if (dp83867->tx_id_delay > DP83867_RGMII_TX_CLK_DELAY_MAX) {
+		if (!ret && dp83867->tx_id_delay > DP83867_RGMII_TX_CLK_DELAY_MAX) {
 			pr_debug("ti,tx-internal-delay value of %u out of range\n",
 				 dp83867->tx_id_delay);
 			return -EINVAL;
-- 
2.51.1