arch/x86: Refactor CAR_GLOBAL quirk for FSP1.0

These platforms return to romstage from FSP only after
already having torn CAR down. A copy of the entire CAR
region is available and discoverable via HOB.

Previously, CBMEM console detected on-the-fly that CAR
migration had happened and relocated cbmem_console_p
accoringlin with car_sync_var(). However, if the CAR_GLOBAL
pointing to another object inside CAR is a relative offset
instead, we have a more generic solution that can be used
with timestamps code as well.

Change-Id: Ica877b47e68d56189e9d998b5630019d4328a419
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35140
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 22 insertions, 27 deletions

diff --git a/src/cpu/x86/car.c b/src/cpu/x86/car.c
index 6fc61686df..009ac192cc 100644
--- a/src/cpu/x86/car.c
+++ b/src/cpu/x86/car.c
@@ -77,41 +77,36 @@ void *car_get_var_ptr(void *var)
 	return &migrated_base[offset];
 }
 
+#if CONFIG(PLATFORM_USES_FSP1_0)
 /*
- * Update a CAR_GLOBAL variable var, originally pointing to CAR region,
- * with the address in migrated CAR region in DRAM.
+ * When a CAR_GLOBAL points to target object inside CAR, use relative
+ * addressing. Such CAR_GLOBAL has to be expicitly accessed using
+ * car_set_reloc_ptr() and car_get_reloc_ptr() as the stored value is now
+ * an offset instead of the absolute address (pointer) of the target.
+ *
+ * This way discovery of objects that are not CAR_GLOBALs themselves,
+ * remain discoverable after CAR migration has implicitly happened.
  */
-void *car_sync_var_ptr(void *var)
+void car_set_reloc_ptr(void *var, void *val)
 {
-	void **mig_var = car_get_var_ptr(var);
-	void *_car_start = _car_relocatable_data_start;
-	void *_car_end = _car_relocatable_data_end;
+	uintptr_t *offset = car_get_var_ptr(var);
+	*offset = 0;
 
-	/* Not moved or migrated yet. */
-	if (mig_var == var)
-		return mig_var;
-
-	/*
-	 * Migrate the cbmem console pointer for FSP 1.0 platforms. Otherwise,
-	 * keep console buffer in CAR until cbmemc_reinit() moves it.
-	 */
-	if (*mig_var == _preram_cbmem_console) {
-		if (CONFIG(PLATFORM_USES_FSP1_0))
-			*mig_var += (char *)mig_var - (char *)var;
-		return mig_var;
-	}
+	if (val)
+		*offset = (uintptr_t)offset - (uintptr_t)val;
+}
 
-	/* It's already pointing outside car.global_data. */
-	if (*mig_var < _car_start || *mig_var > _car_end)
-		return mig_var;
+void *car_get_reloc_ptr(void *var)
+{
+	uintptr_t *offset = car_get_var_ptr(var);
+	void *val = NULL;
 
-	/* Move the pointer by the same amount the variable storing it was
-	 * moved by.
-	 */
-	*mig_var += (char *)mig_var - (char *)var;
+	if (*offset)
+		val = (void *)((uintptr_t)offset - *offset);
 
-	return mig_var;
+	return val;
 }
+#endif
 
 int car_active(void)
 {