cbmem console: Locate the preram console with a symbol instead of a section.

On non-x86 systems, the location of the preram CBMEM console may not be in a
predictable place relative to other things in the linker script. That makes it
difficult to work with as its own section because the linker will complain if
you try to move backwards as it lays out memory. If the console header is
treated as an actual blob of memory which has to be put in the image, we'd
have to predict where to put it so that it isn't before something with a lower
address or after something with a higher address. Symbols, on the other hand,
can be defined arbitrarily.

BUG=None
TEST=Built and booted on link and falco. Spot checked that the CBMEM console
was the same as the output on the serial port.
BRANCH=None

Change-Id: I3257b981eee0c15bb997a9f2c55a03494c6ec6f0
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/193164
Reviewed-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>

src/arch/aarch64/include/arch/early_variables.h

@@ -25,7 +25,6 @@
 #endif
 
 #define CAR_GLOBAL
-#define CAR_CBMEM
 
 #define CAR_MIGRATE(migrate_fn_)
 static inline void *car_get_var_ptr(void *var) { return var; }

src/arch/arm/include/arch/early_variables.h

@@ -25,7 +25,6 @@
 #endif
 
 #define CAR_GLOBAL
-#define CAR_CBMEM
 
 #define CAR_MIGRATE(migrate_fn_)
 static inline void *car_get_var_ptr(void *var) { return var; }

src/arch/x86/include/arch/early_variables.h

@@ -22,10 +22,8 @@
 
 #ifdef __PRE_RAM__
 #define CAR_GLOBAL __attribute__((section(".car.global_data,\"w\",@nobits#")))
-#define CAR_CBMEM __attribute__((section(".car.cbmem_console,\"w\",@nobits#")))
 #else
 #define CAR_GLOBAL
-#define CAR_CBMEM
 #endif
 
 #if CONFIG_CAR_MIGRATION && defined(__PRE_RAM__)

src/arch/x86/init/romstage.ld

@@ -54,15 +54,15 @@ SECTIONS
 	.car.data . (NOLOAD) : {
 		_car_data_start = .;
 		*(.car.global_data);
-		/* The cbmem_console section comes last to take advantage of
-		 * a zero-sized array to hold the memconsole contents that
-		 * grows to a bound of CONFIG_CONSOLE_CAR_BUFFER_SIZE. However,
-		 * collisions within the cache-as-ram region cannot be
+		_car_data_end = .;
+		/* The preram cbmem console area comes last to take advantage
+		 * of a zero-sized array to hold the memconsole contents that
+		 * grows to a bound of CONFIG_CONSOLE_PRERAM_BUFFER_SIZE.
+		 * However, collisions within the cache-as-ram region cannot be
 		 * statically checked because the cache-as-ram region usage is
 		 * cpu/chipset dependent. */
-		*(.car.cbmem_console);
-		_car_data_end = .;
+		preram_cbmem_console = .;
 	}
 
-	_bogus = ASSERT((SIZEOF(.car.data) <= CONFIG_DCACHE_RAM_SIZE), "Cache as RAM area is too full");
+	_bogus = ASSERT((SIZEOF(.car.data) + CONFIG_CONSOLE_PRERAM_BUFFER_SIZE <= CONFIG_DCACHE_RAM_SIZE), "Cache as RAM area is too full");
 }

src/console/Kconfig

@@ -238,15 +238,15 @@ config CONSOLE_CBMEM_BUFFER_SIZE
 	  value (64K or 0x10000 bytes) is large enough to accommodate
 	  even the BIOS_SPEW level.
 
-config CONSOLE_CAR_BUFFER_SIZE
+config CONSOLE_PRERAM_BUFFER_SIZE
 	depends on CONSOLE_CBMEM
-	hex "Room allocated for console output in Cache as RAM"
+	hex "Room allocated for console output before RAM is initialized"
 	default 0xc00
 	help
 	  Console is used before RAM is initialized. This is the room reserved
-	  in the DCACHE based RAM to keep console output before it can be
-	  saved in a CBMEM buffer. 3K bytes should be enough even for the
-	  BIOS_SPEW level.
+	  in the DCACHE based RAM, SRAM, etc. to keep console output before it
+	  can be saved in a CBMEM buffer. 3K bytes should be enough even for
+	  the BIOS_SPEW level.
 
 
 choice

src/lib/cbmem_console.c

@@ -43,7 +43,7 @@ static struct cbmem_console *cbmem_console_p CAR_GLOBAL;
  * the area are defined in the config.
  */
 
-static struct cbmem_console car_cbmem_console CAR_CBMEM;
+extern struct cbmem_console preram_cbmem_console;
 
 /*
  * Once DRAM is initialized and the cache as ram mode is disabled, while still
@@ -114,7 +114,8 @@ static inline void init_console_ptr(void *storage, u32 total_space)
 void cbmemc_init(void)
 {
 #ifdef __PRE_RAM__
-	init_console_ptr(&car_cbmem_console, CONFIG_CONSOLE_CAR_BUFFER_SIZE);
+	init_console_ptr(&preram_cbmem_console,
+			 CONFIG_CONSOLE_PRERAM_BUFFER_SIZE);
 #else
 	/*
 	 * Initializing before CBMEM is available, use static buffer to store