timestamps: Improve collection for ENV_ROMSTAGE_OR_BEFORE

Keep track of the active timestamp table location using
a CAR_GLOBAL variable. Done this way, the entire table
can be located outside _car_relocatable_data and we only
switch the pointer to CBMEM and copy the data before
CAR gets torn down.

Fix comments about requirements of timestamp_init() usage.

Remove timestamp_cache from postcar and ramstage, as CBMEM
is available early on.

Change-Id: I87370f62db23318069b6fd56ba0d1171d619cb8a
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35032
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/car.ld

@@ -56,17 +56,16 @@
 	. += 32;
 	_epdpt = .;
 #endif
-	_car_relocatable_data_start = .;
+
-	/* The timestamp implementation relies on this storage to be around
-	 * after migration. One of the fields indicates not to use it as the
-	 * backing store once cbmem comes online. Therefore, this data needs
-	 * to reside in the migrated area (between _car_relocatable_data_start
-	 * and _car_relocatable_data_end). */
 	TIMESTAMP(., 0x200)
+
+	_car_relocatable_data_start = .;
+
 	_car_ehci_dbg_info_start = .;
 	/* Reserve sizeof(struct ehci_dbg_info). */
         . += 80;
         _car_ehci_dbg_info_end = .;
+
 	/* _car_global_start and _car_global_end provide symbols to per-stage
 	 * variables that are not shared like the timestamp and the pre-ram
 	 * cbmem console. This is useful for clearing this area on a per-stage

src/include/timestamp.h

@@ -21,12 +21,10 @@
 
 #if CONFIG(COLLECT_TIMESTAMPS)
 /*
- * timestamp_init() needs to be called once for each of these cases:
+ * timestamp_init() needs to be called once in *one* of the ENV_ROMSTAGE_OR_BEFORE
- *    1. __PRE_RAM__ (bootblock, romstage, verstage, etc) and
+ * stages (bootblock, romstage, verstage, etc). It's up to the chipset/arch
- *    2. !__PRE_RAM__ (ramstage)
+ * to make the call in the earliest stage, otherwise some timestamps will be lost.
- * The latter is taken care of by the generic coreboot infrastructure so
+ * For x86 ENV_ROMSTAGE call must be made before CAR is torn down.
- * it's up to the chipset/arch to call timestamp_init() in *one* of
- * the __PRE_RAM__ stages. If multiple calls are made timestamps will be lost.
  */
 void timestamp_init(uint64_t base);
 /*

src/lib/hardwaremain.c

@@ -461,9 +461,6 @@ void main(void)
 	 */
 	cbmem_initialize();
 
-	/* Record current time, try to locate timestamps in CBMEM. */
-	timestamp_init(timestamp_get());
-
 	timestamp_add_now(TS_START_RAMSTAGE);
 	post_code(POST_ENTRY_RAMSTAGE);
 

src/lib/timestamp.c

@@ -31,7 +31,6 @@
 #define MAX_BSS_TIMESTAMP_CACHE 16
 
 struct __packed timestamp_cache {
-	uint32_t cache_state;
 	struct timestamp_table table;
 	/* The struct timestamp_table has a 0 length array as its last field.
 	 * The  following 'entries' array serves as the storage space for the
@@ -41,28 +40,23 @@ struct __packed timestamp_cache {
 
 DECLARE_OPTIONAL_REGION(timestamp);
 
-#if defined(__PRE_RAM__)
+#if ENV_ROMSTAGE_OR_BEFORE
 #define USE_TIMESTAMP_REGION (REGION_SIZE(timestamp) > 0)
 #else
 #define USE_TIMESTAMP_REGION 0
 #endif
 
-/* The cache location will sit in BSS when in ramstage/postcar. */
+/* Currently we never store timestamp cache in .bss. */
-#define TIMESTAMP_CACHE_IN_BSS (ENV_RAMSTAGE || ENV_POSTCAR)
+#define TIMESTAMP_CACHE_IN_BSS 0
-
-#define HAS_CBMEM (ENV_ROMSTAGE || ENV_RAMSTAGE || ENV_POSTCAR)
 
 /*
- * Storage of cache entries during ramstage/postcar prior to cbmem coming
+ * Storage of cache entries prior to cbmem coming online.
- * online.
  */
 static struct timestamp_cache timestamp_cache;
 
-enum {
+/* This points to the active timestamp_table and can change within a stage.
-	TIMESTAMP_CACHE_UNINITIALIZED = 0,
+   as CBMEM comes available. */
-	TIMESTAMP_CACHE_INITIALIZED,
+static struct timestamp_table *glob_ts_table CAR_GLOBAL;
-	TIMESTAMP_CACHE_NOT_NEEDED,
-};
 
 static void timestamp_cache_init(struct timestamp_cache *ts_cache,
 				 uint64_t base)
@@ -70,7 +64,6 @@ static void timestamp_cache_init(struct timestamp_cache *ts_cache,
 	ts_cache->table.num_entries = 0;
 	ts_cache->table.max_entries = MAX_BSS_TIMESTAMP_CACHE;
 	ts_cache->table.base_time = base;
-	ts_cache->cache_state = TIMESTAMP_CACHE_INITIALIZED;
 
 	if (USE_TIMESTAMP_REGION)
 		ts_cache->table.max_entries = (REGION_SIZE(timestamp) -
@@ -87,7 +80,7 @@ static struct timestamp_cache *timestamp_cache_get(void)
 	} else if (USE_TIMESTAMP_REGION) {
 		if (REGION_SIZE(timestamp) < sizeof(*ts_cache))
 			BUG();
-		ts_cache = car_get_var_ptr((void *)_timestamp);
+		ts_cache = (void *)_timestamp;
 	}
 
 	return ts_cache;
@@ -128,33 +121,26 @@ static int timestamp_should_run(void)
 
 static struct timestamp_table *timestamp_table_get(void)
 {
-	MAYBE_STATIC_BSS struct timestamp_table *ts_table = NULL;
+	struct timestamp_table *ts_table;
 	struct timestamp_cache *ts_cache;
 
-	if (ts_table != NULL)
+	ts_table = car_get_ptr(glob_ts_table);
+	if (ts_table)
 		return ts_table;
 
 	ts_cache = timestamp_cache_get();
+	if (ts_cache)
+		ts_table = &ts_cache->table;
 
-	if (ts_cache == NULL) {
+	car_set_ptr(glob_ts_table, ts_table);
-		if (HAS_CBMEM)
-			ts_table = cbmem_find(CBMEM_ID_TIMESTAMP);
-		return ts_table;
-	}
-
-	/* Cache is required. */
-	if (ts_cache->cache_state != TIMESTAMP_CACHE_NOT_NEEDED)
-		return &ts_cache->table;
-
-	/* Cache shouldn't be used but there's no backing store. */
-	if (!HAS_CBMEM)
-		return NULL;
-
-	ts_table = cbmem_find(CBMEM_ID_TIMESTAMP);
-
 	return ts_table;
 }
 
+static void timestamp_table_set(struct timestamp_table *ts)
+{
+	car_set_ptr(glob_ts_table, ts);
+}
+
 static const char *timestamp_name(enum timestamp_id id)
 {
 	int i;
@@ -212,6 +198,8 @@ void timestamp_init(uint64_t base)
 {
 	struct timestamp_cache *ts_cache;
 
+	assert(ENV_ROMSTAGE_OR_BEFORE);
+
 	if (!timestamp_should_run())
 		return;
 
@@ -222,36 +210,19 @@ void timestamp_init(uint64_t base)
 		return;
 	}
 
-	/* Timestamps could have already been recovered.
-	 * In those circumstances honor the cache which sits in BSS
-	 * as it has already been initialized. */
-	if (TIMESTAMP_CACHE_IN_BSS &&
-	    ts_cache->cache_state != TIMESTAMP_CACHE_UNINITIALIZED)
-		return;
-
 	timestamp_cache_init(ts_cache, base);
+	timestamp_table_set(&ts_cache->table);
 }
 
 static void timestamp_sync_cache_to_cbmem(int is_recovery)
 {
 	uint32_t i;
-	struct timestamp_cache *ts_cache;
 	struct timestamp_table *ts_cache_table;
-	struct timestamp_table *ts_cbmem_table = NULL;
+	struct timestamp_table *ts_cbmem_table;
 
 	if (!timestamp_should_run())
 		return;
 
-	ts_cache = timestamp_cache_get();
-
-	/* No timestamp cache found */
-	if (ts_cache == NULL) {
-		printk(BIOS_ERR, "ERROR: No timestamp cache found\n");
-		return;
-	}
-
-	ts_cache_table = &ts_cache->table;
-
 	/* cbmem is being recovered. */
 	if (is_recovery) {
 		/* x86 resume path expects timestamps to be reset. */
@@ -270,6 +241,19 @@ static void timestamp_sync_cache_to_cbmem(int is_recovery)
 
 	if (ts_cbmem_table == NULL) {
 		printk(BIOS_ERR, "ERROR: No timestamp table allocated\n");
+		timestamp_table_set(NULL);
+		return;
+	}
+
+	/* Seed the timestamp tick frequency in ENV_PAYLOAD_LOADER. */
+	if (ENV_PAYLOAD_LOADER)
+		ts_cbmem_table->tick_freq_mhz = timestamp_tick_freq_mhz();
+
+	ts_cache_table = timestamp_table_get();
+	if (!ts_cache_table) {
+		if (ENV_ROMSTAGE)
+			printk(BIOS_ERR, "ERROR: No timestamp cache found\n");
+		timestamp_table_set(ts_cbmem_table);
 		return;
 	}
 
@@ -294,6 +278,7 @@ static void timestamp_sync_cache_to_cbmem(int is_recovery)
 	 * If timestamps only get initialized in ramstage, the base_time from
 	 * timestamp_init() will get ignored and all timestamps will be 0-based.
 	 */
+
 	for (i = 0; i < ts_cache_table->num_entries; i++) {
 		struct timestamp_entry *tse = &ts_cache_table->entries[i];
 		timestamp_add_table_entry(ts_cbmem_table, tse->entry_id,
@@ -304,13 +289,9 @@ static void timestamp_sync_cache_to_cbmem(int is_recovery)
 	if (ts_cbmem_table->base_time == 0)
 		ts_cbmem_table->base_time = ts_cache_table->base_time;
 
-	/* Seed the timestamp tick frequency in ENV_PAYLOAD_LOADER. */
-	if (ENV_PAYLOAD_LOADER)
-		ts_cbmem_table->tick_freq_mhz = timestamp_tick_freq_mhz();
-
 	/* Cache no longer required. */
+	timestamp_table_set(ts_cbmem_table);
 	ts_cache_table->num_entries = 0;
-	ts_cache->cache_state = TIMESTAMP_CACHE_NOT_NEEDED;
 }
 
 void timestamp_rescale_table(uint16_t N, uint16_t M)