intel/fsp2_0: Add fsp2.1 shared stack feature support

FSP 2.1 implementation is adding features on top of fsp2_0.
One such feature is a shared stack implementation that requires
coreboot to allocate stack for fspm and then fsp uses the same
stack as coreboot. This implementation adds support for shared
stack feature.

Change-Id: I6581111dbaddfa403eca14100577ccc8a05c4ec7
Signed-off-by: Aamir Bohra <aamir.bohra@intel.com>
Reviewed-on: https://review.coreboot.org/28358
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/drivers/intel/fsp2_0/Kconfig

@@ -97,6 +97,15 @@ config FSP_M_XIP
 	help
 	  Select this value when FSP-M is execute-in-place.
 
+config FSP_USES_CB_STACK
+	bool
+	default n
+	help
+	  Enable support for fsp to use same stack as coreboot.
+	  This option allows fsp to continue using coreboot stack
+	  without reinitializing stack pointer. This feature is
+	  supported Icelake onwards.
+
 config VERIFY_HOBS
 	bool "Verify the FSP hand-off-blocks"
 	default n

src/drivers/intel/fsp2_0/memory_init.c

@@ -165,27 +165,44 @@ static enum cb_err check_region_overlap(const struct memranges *ranges,
 
 	return CB_SUCCESS;
 }
-
+static enum cb_err setup_fsp_stack_frame(FSPM_ARCH_UPD *arch_upd,
-static enum cb_err fsp_fill_common_arch_params(FSPM_ARCH_UPD *arch_upd,
+		const struct memranges *memmap)
-					bool s3wake, uint32_t fsp_version,
-					const struct memranges *memmap)
 {
 	uintptr_t stack_begin;
 	uintptr_t stack_end;
 
 	/*
-	 * FSPM_UPD passed here is populated with default values provided by
+	 * FSP 2.1 version would use same stack as coreboot instead of
-	 * the blob itself. We let FSPM use top of CAR region of the size it
+	 * setting up seprate stack frame. FSP 2.1 would not relocate stack
-	 * requests.
+	 * top and does not reinitialize stack pointer.
+	 */
+	if (IS_ENABLED(CONFIG_FSP_USES_CB_STACK)) {
+		arch_upd->StackBase = (void *)_car_stack_end;
+		arch_upd->StackSize = CONFIG_DCACHE_BSP_STACK_SIZE;
+		return CB_SUCCESS;
+	}
+
+	/*
+	 * 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.
 	 */
 	stack_end = (uintptr_t)_car_region_end;
 	stack_begin = stack_end - arch_upd->StackSize;
-
 	if (check_region_overlap(memmap, "FSPM stack", stack_begin,
 				stack_end) != CB_SUCCESS)
 		return CB_ERR;
 
 	arch_upd->StackBase = (void *)stack_begin;
+	return CB_SUCCESS;
+}
+
+static enum cb_err fsp_fill_common_arch_params(FSPM_ARCH_UPD *arch_upd,
+					bool s3wake, uint32_t fsp_version,
+					const struct memranges *memmap)
+{
+	if (setup_fsp_stack_frame(arch_upd, memmap))
+		return CB_ERR;
 
 	fsp_fill_mrc_cache(arch_upd, fsp_version);