net: ethernet: mtk_eth_soc: remove incorrect PLL configuration

MT7623 GMAC0 attempts to configure the system clocking according to the
required speed in the .mac_config callback for non-SGMII, non-baseX and
non-TRGMII modes.

state->speed setting has never been reliable in the .mac_config
callback - there are cases where this is not the link speed,
particularly via ethtool paths, so this has always been unreliable (as
detailed in phylink's documentation.)

There is the additional issue that mtk_gmac0_rgmii_adjust() will only
be called if state->interface changes, which means it only configures
the system clocking on the very first .mac_config call, which will be
made when the network device is first brought up before any link is
established.

Essentially, this code is incredibly buggy, and probably never worked.

Moreover, checking the in-kernel DT files, it seems no platform makes
use of this code path.

Therefore, let's remove it, and disable interface modes for port 0 that
are not SGMII, 1000base-X, 2500base-X or TRGMII on the MT7623.
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -385,10 +385,8 @@ static int mt7621_gmac0_rgmii_adjust(struct mtk_eth *eth,
 }
 
 static void mtk_gmac0_rgmii_adjust(struct mtk_eth *eth,
-				   phy_interface_t interface, int speed)
+				   phy_interface_t interface)
 {
-	unsigned long rate;
-	u32 tck, rck, intf;
 	int ret;
 
 	if (interface == PHY_INTERFACE_MODE_TRGMII) {
@@ -399,30 +397,7 @@ static void mtk_gmac0_rgmii_adjust(struct mtk_eth *eth,
 		return;
 	}
 
-	if (speed == SPEED_1000) {
-		intf = INTF_MODE_RGMII_1000;
-		rate = 250000000;
-		rck = RCK_CTRL_RGMII_1000;
-		tck = TCK_CTRL_RGMII_1000;
-	} else {
-		intf = INTF_MODE_RGMII_10_100;
-		rate = 500000000;
-		rck = RCK_CTRL_RGMII_10_100;
-		tck = TCK_CTRL_RGMII_10_100;
-	}
-
-	mtk_w32(eth, intf, INTF_MODE);
-
-	regmap_update_bits(eth->ethsys, ETHSYS_CLKCFG0,
-			   ETHSYS_TRGMII_CLK_SEL362_5,
-			   ETHSYS_TRGMII_CLK_SEL362_5);
-
-	ret = clk_set_rate(eth->clks[MTK_CLK_TRGPLL], rate);
-	if (ret)
-		dev_err(eth->dev, "Failed to set trgmii pll: %d\n", ret);
-
-	mtk_w32(eth, rck, TRGMII_RCK_CTRL);
-	mtk_w32(eth, tck, TRGMII_TCK_CTRL);
+	dev_err(eth->dev, "Missing PLL configuration, ethernet may not work\n");
 }
 
 static struct phylink_pcs *mtk_mac_select_pcs(struct phylink_config *config,
@@ -498,17 +473,8 @@ static void mtk_mac_config(struct phylink_config *config, unsigned int mode,
 							      state->interface))
 					goto err_phy;
 			} else {
-				/* FIXME: this is incorrect. Not only does it
-				 * use state->speed (which is not guaranteed
-				 * to be correct) but it also makes use of it
-				 * in a code path that will only be reachable
-				 * when the PHY interface mode changes, not
-				 * when the speed changes. Consequently, RGMII
-				 * is probably broken.
-				 */
 				mtk_gmac0_rgmii_adjust(mac->hw,
-						       state->interface,
-						       state->speed);
+						       state->interface);
 
 				/* mt7623_pad_clk_setup */
 				for (i = 0 ; i < NUM_TRGMII_CTRL; i++)
@@ -4366,13 +4332,19 @@ static int mtk_add_mac(struct mtk_eth *eth, struct device_node *np)
 	mac->phylink_config.mac_capabilities = MAC_ASYM_PAUSE | MAC_SYM_PAUSE |
 		MAC_10 | MAC_100 | MAC_1000 | MAC_2500FD;
 
-	__set_bit(PHY_INTERFACE_MODE_MII,
-		  mac->phylink_config.supported_interfaces);
-	__set_bit(PHY_INTERFACE_MODE_GMII,
-		  mac->phylink_config.supported_interfaces);
+	/* MT7623 gmac0 is now missing its speed-specific PLL configuration
+	 * in its .mac_config method (since state->speed is not valid there.
+	 * Disable support for MII, GMII and RGMII.
+	 */
+	if (!mac->hw->soc->disable_pll_modes || mac->id != 0) {
+		__set_bit(PHY_INTERFACE_MODE_MII,
+			  mac->phylink_config.supported_interfaces);
+		__set_bit(PHY_INTERFACE_MODE_GMII,
+			  mac->phylink_config.supported_interfaces);
 
-	if (MTK_HAS_CAPS(mac->hw->soc->caps, MTK_RGMII))
-		phy_interface_set_rgmii(mac->phylink_config.supported_interfaces);
+		if (MTK_HAS_CAPS(mac->hw->soc->caps, MTK_RGMII))
+			phy_interface_set_rgmii(mac->phylink_config.supported_interfaces);
+	}
 
 	if (MTK_HAS_CAPS(mac->hw->soc->caps, MTK_TRGMII) && !mac->id)
 		__set_bit(PHY_INTERFACE_MODE_TRGMII,
@@ -4845,6 +4817,7 @@ static const struct mtk_soc_data mt7623_data = {
 	.offload_version = 1,
 	.hash_offset = 2,
 	.foe_entry_size = MTK_FOE_ENTRY_V1_SIZE,
+	.disable_pll_modes = true,
 	.txrx = {
 		.txd_size = sizeof(struct mtk_tx_dma),
 		.rxd_size = sizeof(struct mtk_rx_dma),

drivers/net/ethernet/mediatek/mtk_eth_soc.h

@@ -1030,6 +1030,7 @@ struct mtk_soc_data {
 	u16		foe_entry_size;
 	netdev_features_t hw_features;
 	bool		has_accounting;
+	bool		disable_pll_modes;
 	struct {
 		u32	txd_size;
 		u32	rxd_size;