x86: Correct mrccache find_next_mrc_cache() calculation

This should take account of the end of the new cache record since a record
cannot extend beyond the end of the flash region. This problem was not
seen before due to the alignment of the relatively small amount of MRC
data.

But with Apollo Lake the MRC data is about 45KB, even if most of it is
zeroes.

Fix this bug and update the parameter name to be less confusing.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

arch/x86/lib/mrccache.c

@@ -80,21 +80,31 @@ struct mrc_data_container *mrccache_find_current(struct mrc_region *entry)
 /**
  * find_next_mrc_cache() - get next cache entry
  *
+ * This moves to the next cache entry in the region, making sure it has enough
+ * space to hold data of size @data_size.
+ *
  * @entry:	MRC cache flash area
  * @cache:	Entry to start from
+ * @data_size:	Required data size of the new entry. Note that we assume that
+ *	all cache entries are the same size
  *
  * @return next cache entry if found, NULL if we got to the end
  */
 static struct mrc_data_container *find_next_mrc_cache(struct mrc_region *entry,
-		struct mrc_data_container *cache)
+		struct mrc_data_container *prev, int data_size)
 {
+	struct mrc_data_container *cache;
 	ulong base_addr, end_addr;
 
 	base_addr = entry->base + entry->offset;
 	end_addr = base_addr + entry->length;
 
-	cache = next_mrc_block(cache);
-	if ((ulong)cache >= end_addr) {
+	/*
+	 * We assume that all cache entries are the same size, but let's use
+	 * data_size here for clarity.
+	 */
+	cache = next_mrc_block(prev);
+	if ((ulong)cache + mrc_block_size(data_size) > end_addr) {
 		/* Crossed the boundary */
 		cache = NULL;
 		debug("%s: no available entries found\n", __func__);
@@ -131,7 +141,7 @@ int mrccache_update(struct udevice *sf, struct mrc_region *entry,
 
 	/* Move to the next block, which will be the first unused block */
 	if (cache)
-		cache = find_next_mrc_cache(entry, cache);
+		cache = find_next_mrc_cache(entry, cache, cur->data_size);
 
 	/*
 	 * If we have got to the end, erase the entire mrc-cache area and start