Some SoCs are just validated with the TX delay enabled. With commit
ca13b249f291 ("net: ethernet: ti: am65-cpsw: fixup PHY mode for fixed
RGMII TX delay"), the network driver will patch the delay setting on the
fly assuming that the TX delay is fixed. In reality, the TX delay is
configurable and just skipped in the documentation. There are
bootloaders, which will disable the TX delay and this will lead to a
transmit path which doesn't add any delays at all. Fix that by always
forcing the TX delay to be enabled.

Fixes: ca13b249f291 ("net: ethernet: ti: am65-cpsw: fixup PHY mode for fixed RGMII TX delay")
Signed-off-by: Michael Walle <mwalle@kernel.org>
---
 drivers/phy/ti/phy-gmii-sel.c | 52 +++++++++++++++++++++++++++++------
 1 file changed, 44 insertions(+), 8 deletions(-)

diff --git a/drivers/phy/ti/phy-gmii-sel.c b/drivers/phy/ti/phy-gmii-sel.c
index ff5d5e29629f..a0c19d00ff3a 100644
--- a/drivers/phy/ti/phy-gmii-sel.c
+++ b/drivers/phy/ti/phy-gmii-sel.c
@@ -34,6 +34,7 @@ enum {
 	PHY_GMII_SEL_PORT_MODE = 0,
 	PHY_GMII_SEL_RGMII_ID_MODE,
 	PHY_GMII_SEL_RMII_IO_CLK_EN,
+	PHY_GMII_SEL_FIXED_TX_DELAY,
 	PHY_GMII_SEL_LAST,
 };
 
@@ -127,6 +128,16 @@ static int phy_gmii_sel_mode(struct phy *phy, enum phy_mode mode, int submode)
 		goto unsupported;
 	}
 
+	/*
+	 * Some SoCs only support fixed MAC side TX delays. According to the
+	 * datasheet, they are always enabled, but that turns out not to be the
+	 * case and the delay is configurable. But according to the vendor that
+	 * mode is not validated and might not work. Some bootloaders disable
+	 * that bit. To work around that enable it again.
+	 */
+	if (soc_data->features & BIT(PHY_GMII_SEL_FIXED_TX_DELAY))
+		rgmii_id = 0;
+
 	if_phy->phy_if_mode = submode;
 
 	dev_dbg(dev, "%s id:%u mode:%u rgmii_id:%d rmii_clk_ext:%d\n",
@@ -210,25 +221,46 @@ struct phy_gmii_sel_soc_data phy_gmii_sel_soc_dm814 = {
 
 static const
 struct reg_field phy_gmii_sel_fields_am654[][PHY_GMII_SEL_LAST] = {
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x0, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x4, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x8, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0xC, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x10, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x14, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x18, 0, 2), },
-	{ [PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x1C, 0, 2), },
+	{
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x0, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x0, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x4, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x4, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x8, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x8, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0xC, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0xC, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x10, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x10, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x14, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x14, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x18, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x18, 4, 4),
+	}, {
+		[PHY_GMII_SEL_PORT_MODE] = REG_FIELD(0x1C, 0, 2),
+		[PHY_GMII_SEL_RGMII_ID_MODE] = REG_FIELD(0x1C, 4, 4),
+	},
 };
 
 static const
 struct phy_gmii_sel_soc_data phy_gmii_sel_soc_am654 = {
 	.use_of_data = true,
+	.features = BIT(PHY_GMII_SEL_RGMII_ID_MODE) |
+		    BIT(PHY_GMII_SEL_FIXED_TX_DELAY),
 	.regfields = phy_gmii_sel_fields_am654,
 };
 
 static const
 struct phy_gmii_sel_soc_data phy_gmii_sel_cpsw5g_soc_j7200 = {
 	.use_of_data = true,
+	.features = BIT(PHY_GMII_SEL_RGMII_ID_MODE) |
+		    BIT(PHY_GMII_SEL_FIXED_TX_DELAY),
 	.regfields = phy_gmii_sel_fields_am654,
 	.extra_modes = BIT(PHY_INTERFACE_MODE_QSGMII) | BIT(PHY_INTERFACE_MODE_SGMII) |
 		       BIT(PHY_INTERFACE_MODE_USXGMII),
@@ -239,6 +271,8 @@ struct phy_gmii_sel_soc_data phy_gmii_sel_cpsw5g_soc_j7200 = {
 static const
 struct phy_gmii_sel_soc_data phy_gmii_sel_cpsw9g_soc_j721e = {
 	.use_of_data = true,
+	.features = BIT(PHY_GMII_SEL_RGMII_ID_MODE) |
+		    BIT(PHY_GMII_SEL_FIXED_TX_DELAY),
 	.regfields = phy_gmii_sel_fields_am654,
 	.extra_modes = BIT(PHY_INTERFACE_MODE_QSGMII) | BIT(PHY_INTERFACE_MODE_SGMII),
 	.num_ports = 8,
@@ -248,6 +282,8 @@ struct phy_gmii_sel_soc_data phy_gmii_sel_cpsw9g_soc_j721e = {
 static const
 struct phy_gmii_sel_soc_data phy_gmii_sel_cpsw9g_soc_j784s4 = {
 	.use_of_data = true,
+	.features = BIT(PHY_GMII_SEL_RGMII_ID_MODE) |
+		    BIT(PHY_GMII_SEL_FIXED_TX_DELAY),
 	.regfields = phy_gmii_sel_fields_am654,
 	.extra_modes = BIT(PHY_INTERFACE_MODE_QSGMII) | BIT(PHY_INTERFACE_MODE_SGMII) |
 		       BIT(PHY_INTERFACE_MODE_USXGMII),
-- 
2.39.5