sb/intel/bd82x6x: Handle enabling of GbE

The integrated GbE port is toggled via the Backed-Up Control (BUC)
register. We already disable it according to the devicetree setting
but never enabled it. This could lead to the confusing situation
that it was disabled before (different build, vendor BIOS, etc.)
but shouldn't be anymore.

As we need a full reset after enabling GbE, do it in early PCH init.

Change-Id: I9db3d1923684b938d2c9f5b369b0953570c7fc15
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36902
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/intel/dcp847ske/early_southbridge.c

@@ -33,16 +33,6 @@ void mainboard_late_rcba_config(void)
 	/* Disable devices */
 	RCBA32(FD) |= PCH_DISABLE_P2P;
 
-#if CONFIG(USE_NATIVE_RAMINIT)
-	/* Enable Gigabit Ethernet */
-	if (RCBA32(BUC) & PCH_DISABLE_GBE) {
-		RCBA32(BUC) &= ~PCH_DISABLE_GBE;
-		/* Datasheet says clearing the bit requires a reset after */
-		printk(BIOS_DEBUG, "Enabled gigabit ethernet, reset once.\n");
-		full_reset();
-	}
-#endif
-
 	/* Set "mobile" bit in MCH (which makes sense layout-wise). */
 	/* Note sure if this has any effect at all though. */
 	MCHBAR32(0x0004) |= 0x00001000;

src/southbridge/intel/bd82x6x/early_pch.c

@@ -16,6 +16,7 @@
 #include <device/mmio.h>
 #include <device/pci_ops.h>
 #include <arch/cbfs.h>
+#include <cf9_reset.h>
 #include <ip_checksum.h>
 #include <device/pci_def.h>
 #include <southbridge/intel/common/gpio.h>
@@ -253,6 +254,30 @@ static void pch_generic_setup(void)
 	write_pmbase16(TCO1_CNT, 1 << 11);	/* halt timer */
 }
 
+static void pch_enable_gbe(void)
+{
+	uint8_t wanted_buc;
+
+	/* Don't do this in the bootblock, it might be RO. So one
+	   couldn't change the setting later in an updated romstage. */
+	if (ENV_BOOTBLOCK)
+		return;
+
+	const struct device *const gbe = pcidev_on_root(0x19, 0);
+	if (gbe && gbe->enabled)
+		wanted_buc = RCBA8(BUC) & ~PCH_DISABLE_GBE;
+	else
+		wanted_buc = RCBA8(BUC) | PCH_DISABLE_GBE;
+
+	if (RCBA8(BUC) != wanted_buc) {
+		RCBA8(BUC) = wanted_buc;
+		/* Be double sure not to reset for naught. */
+		if (RCBA8(BUC) != wanted_buc)
+			return;
+		full_reset();
+	}
+}
+
 static void pch_enable_lpc_decode(void)
 {
 	/*
@@ -292,7 +317,6 @@ __weak void mainboard_pch_lpc_setup(void)
 
 void early_pch_init(void)
 {
-
 	pch_enable_lpc_decode();
 
 	mainboard_pch_lpc_setup();
@@ -301,5 +325,7 @@ void early_pch_init(void)
 
 	pch_generic_setup();
 
+	pch_enable_gbe();
+
 	setup_pch_gpios(&mainboard_gpio_map);
 }

src/southbridge/intel/bd82x6x/pch.c

@@ -166,7 +166,7 @@ static void pch_hide_devfn(unsigned int devfn)
 		RCBA32_OR(FD2, PCH_DISABLE_KT);
 		break;
 	case PCI_DEVFN(25, 0): /* Gigabit Ethernet */
-		RCBA32_OR(BUC, PCH_DISABLE_GBE);
+		/* BUC is already handled in `early_pch.c`. */
 		break;
 	case PCI_DEVFN(26, 0): /* EHCI #2 */
 		RCBA32_OR(FD, PCH_DISABLE_EHCI2);