soc/intel/apollolake: Avoid hardcoding CAR region size for FSPM

Instead of having to supply CAR memory region during compilation
time it is possible to determine it in runtime. FSP2.0 blobs carry
a copy of UPD structure pre-populated with 'default' values. The
default value for StackSize is actually the real value blob needs.

Change-Id: I298e07bb12470ce659f63846ab096189138e594f
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/14001
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Kconfig

@@ -98,10 +98,4 @@ config ROMSTAGE_ADDR
 	help
 	  The base address (in CAR) where romstage should be linked
 
-config FSPM_STACK_SIZE
-	hex
-	default 0x40000
-	help
-	  The amount of CAR memory FSPM needs. Recommended at least 256KiB
-
 endif

src/soc/intel/apollolake/romstage.c

@@ -141,10 +141,14 @@ void platform_fsp_memory_init_params_cb(struct FSPM_UPD *mupd)
 	mupd->FspmConfig.FitTablePtr = read32((void*) FIT_POINTER);
 	/* Reserve enough memory under TOLUD to save CBMEM header */
 	mupd->FspmArchUpd.BootLoaderTolumSize = cbmem_overhead_size();
-	/* Let FSPM use memory right at the top of CAR */
-	/* TODO: Add checks to see if we collide with other areas */
-	mupd->FspmArchUpd.StackBase = _car_region_end - CONFIG_FSPM_STACK_SIZE;
-	mupd->FspmArchUpd.StackSize = CONFIG_FSPM_STACK_SIZE;
+	/*
+	 * FSPM_UPD passed here is populated with default values provided by
+	 * the blob itself. We let FSPM use top of CAR region of the size it
+	 * requests.
+	 * TODO: add checks to avoid overlap/conflict of CAR usage.
+	 */
+	mupd->FspmArchUpd.StackBase = _car_region_end -
+					mupd->FspmArchUpd.StackSize;
 }
 
 __attribute__ ((weak))