cpu/x86/smm: Define single smm_subregion()

At the moment we only have two splitting of TSEG,
one with and one without IED. They can all use
same implementation.

Make configuration problems of TSEG region assertion
failures.

Rename file from stage_cache.c to tseg_region.c to
reflect it's purpose.

Change-Id: I9daf0dec8fbaaa1f4e6004ea034869f43412d7d5
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34776
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: David Guckian
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/amd/stoneyridge/ramtop.c b/src/soc/amd/stoneyridge/ramtop.c
index e2b0f7d..09af7e4 100644
--- a/src/soc/amd/stoneyridge/ramtop.c
+++ b/src/soc/amd/stoneyridge/ramtop.c
@@ -81,12 +81,6 @@
 	return CONFIG_SMM_TSEG_SIZE;
 }
 
-void smm_region(uintptr_t *start, size_t *size)
-{
-	*start = smm_region_start();
-	*size = smm_region_size();
-}
-
 /*
  * For data stored in TSEG, ensure TValid is clear so R/W access can reach
  * the DRAM when not in SMM.
@@ -109,38 +103,15 @@
 	wrmsr(SMM_MASK_MSR, mask);
 }
 
-int smm_subregion(int sub, uintptr_t *start, size_t *size)
+void smm_region(uintptr_t *start, size_t *size)
 {
 	static int once;
-	uintptr_t sub_base;
-	size_t sub_size;
-	const size_t cache_size = CONFIG_SMM_RESERVED_SIZE;
 
-	smm_region(&sub_base, &sub_size);
-	assert(sub_size > CONFIG_SMM_RESERVED_SIZE);
+	*start = smm_region_start();
+	*size = smm_region_size();
 
 	if (!once) {
 		clear_tvalid();
 		once = 1;
 	}
-
-	switch (sub) {
-	case SMM_SUBREGION_HANDLER:
-		/* Handler starts at the base of TSEG. */
-		sub_size -= cache_size;
-		break;
-	case SMM_SUBREGION_CACHE:
-		/* External cache is in the middle of TSEG. */
-		sub_base += sub_size - cache_size;
-		sub_size = cache_size;
-		break;
-	default:
-		*start = 0;
-		*size = 0;
-		return -1;
-	}
-
-	*start = sub_base;
-	*size = sub_size;
-	return 0;
 }