net: dsa: mt7530: move enabling disabling core clock to mt7530_pll_setup()

Split the code that enables and disables TRGMII clocks and core clock.
Move enabling and disabling core clock to mt7530_pll_setup() as it's
supposed to be run there.

Add 20 ms delay before enabling the core clock as seen on the U-Boot
MediaTek ethernet driver.

Change the comment for enabling and disabling TRGMII clocks as the code
seems to affect both TXC and RXC.

Tested rgmii and trgmii modes of port 6 and rgmii mode of port 5 on MCM
MT7530 on MT7621AT Unielec U7621-06 and standalone MT7530 on MT7623NI
Bananapi BPI-R2.

Fixes: b8f126a8 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Link: https://source.denx.de/u-boot/u-boot/-/blob/29a48bf9ccba45a5e560bb564bbe76e42629325f/drivers/net/mtk_eth.c#L589Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Link: https://lore.kernel.org/r/20230320190520.124513-1-arinc.unal@arinc9.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mt7530.c

@@ -396,6 +396,9 @@ mt7530_fdb_write(struct mt7530_priv *priv, u16 vid,
 /* Set up switch core clock for MT7530 */
 static void mt7530_pll_setup(struct mt7530_priv *priv)
 {
+	/* Disable core clock */
+	core_clear(priv, CORE_TRGMII_GSW_CLK_CG, REG_GSWCK_EN);
+
 	/* Disable PLL */
 	core_write(priv, CORE_GSWPLL_GRP1, 0);
 
@@ -409,6 +412,11 @@ static void mt7530_pll_setup(struct mt7530_priv *priv)
 		   RG_GSWPLL_EN_PRE |
 		   RG_GSWPLL_POSDIV_200M(2) |
 		   RG_GSWPLL_FBKDIV_200M(32));
+
+	udelay(20);
+
+	/* Enable core clock */
+	core_set(priv, CORE_TRGMII_GSW_CLK_CG, REG_GSWCK_EN);
 }
 
 /* Setup TX circuit including relevant PAD and driving */
@@ -466,9 +474,8 @@ mt7530_pad_clk_setup(struct dsa_switch *ds, phy_interface_t interface)
 			mt7530_write(priv, MT7530_TRGMII_TD_ODT(i),
 				     TD_DM_DRVP(8) | TD_DM_DRVN(8));
 
-		/* Disable MT7530 core and TRGMII Tx clocks */
-		core_clear(priv, CORE_TRGMII_GSW_CLK_CG,
-			   REG_GSWCK_EN | REG_TRGMIICK_EN);
+		/* Disable the MT7530 TRGMII clocks */
+		core_clear(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
 
 		/* Setup the MT7530 TRGMII Tx Clock */
 		core_write(priv, CORE_PLL_GROUP5, RG_LCDDS_PCW_NCPO1(ncpo1));
@@ -485,9 +492,8 @@ mt7530_pad_clk_setup(struct dsa_switch *ds, phy_interface_t interface)
 			   RG_LCDDS_PCW_NCPO_CHG | RG_LCCDS_C(3) |
 			   RG_LCDDS_PWDB | RG_LCDDS_ISO_EN);
 
-		/* Enable MT7530 core and TRGMII Tx clocks */
-		core_set(priv, CORE_TRGMII_GSW_CLK_CG,
-			 REG_GSWCK_EN | REG_TRGMIICK_EN);
+		/* Enable the MT7530 TRGMII clocks */
+		core_set(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
 	} else {
 		for (i = 0 ; i < NUM_TRGMII_CTRL; i++)
 			mt7530_rmw(priv, MT7530_TRGMII_RD(i),