arch/x86: Enable ebda library for romstage and postcar

This patch provides a kconfig option as EARLY_EBDA_INIT to
ensures user can make use of EBDA library even during early
boot stages like romstage, postcar.

Change-Id: I603800a531f56b6ebd460d5951c35a645fbfe492
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/21388
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/arch/x86/Kconfig

@@ -135,6 +135,15 @@ config PRERAM_CBMEM_CONSOLE_SIZE
 	help
 	  Increase this value if preram cbmem console is getting truncated
 
+config EARLY_EBDA_INIT
+	bool
+	default n
+	help
+	  Initialize BIOS EBDA area early in romstage to allow bootloader to
+	  use this region for storing data which can be available across
+	  various stages. If user is selecting this option then its users
+	  responsibility to perform EBDA initialization call during romstage.
+
 config PC80_SYSTEM
 	bool
 	default y if ARCH_X86

src/arch/x86/Makefile.inc

@@ -209,6 +209,7 @@ romstage-y += boot.c
 romstage-y += cbmem.c
 romstage-y += cbfs_and_run.c
 romstage-$(CONFIG_ARCH_RAMSTAGE_X86_32) += cpu_common.c
+romstage-$(CONFIG_EARLY_EBDA_INIT) += ebda.c
 romstage-y += memcpy.c
 romstage-y += memmove.c
 romstage-y += memset.c
@@ -283,6 +284,7 @@ postcar-y += boot.c
 postcar-y += cbfs_and_run.c
 postcar-y += cbmem.c
 postcar-y += cpu_common.c
+postcar-$(CONFIG_EARLY_EBDA_INIT) += ebda.c
 postcar-y += exit_car.S
 postcar-y += memcpy.c
 postcar-y += memmove.c

src/arch/x86/include/arch/ebda.h

@@ -17,6 +17,9 @@
 #ifndef __ARCH_EBDA_H
 #define __ARCH_EBDA_H
 
+#include <stdint.h>
+#include <stddef.h>
+
 #define X86_BDA_SIZE		0x200
 #define X86_BDA_BASE		((void *)0x400)
 #define X86_EBDA_SEGMENT	((void *)0x40e)

src/device/device.c

@@ -1179,8 +1179,13 @@ void dev_initialize(void)
 	printk(BIOS_INFO, "Initializing devices...\n");
 
 #if IS_ENABLED(CONFIG_ARCH_X86)
-	/* Ensure EBDA is prepared before Option ROMs. */
-	setup_default_ebda();
+	/*
+	 * Initialize EBDA area in ramstage if early
+	 * initialization is not done.
+	 */
+	if (!IS_ENABLED(CONFIG_EARLY_EBDA_INIT))
+		/* Ensure EBDA is prepared before Option ROMs. */
+		setup_default_ebda();
 #endif
 
 	/* First call the mainboard init. */