commonlib/mem_pool: Allow configuring the alignment

AMD platforms require the destination to be 64 byte aligned in order to
use the SPI DMA controller. This is enforced by the destination address
register because the first 6 bits are marked as reserved.

This change adds an option to the mem_pool so the alignment can be
configured.

BUG=b:179699789
TEST=Boot guybrush to OS

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I8d77ffe4411f86c54450305320c9f52ab41a3075
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56580
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/commonlib/include/commonlib/mem_pool.h

@@ -3,6 +3,7 @@
 #ifndef _MEM_POOL_H_
 #define _MEM_POOL_H_
 
+#include <assert.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -16,23 +17,23 @@
  * were chosen to optimize for the CBFS cache case which may need two buffers
  * to map a single compressed file, and will free them in reverse order.)
  *
- * The memory returned by allocations are at least 8 byte aligned. Note
+ * You must ensure the backing buffer is 'alignment' aligned.
- * that this requires the backing buffer to start on at least an 8 byte
- * alignment.
  */
 
 struct mem_pool {
 	uint8_t *buf;
 	size_t size;
+	size_t alignment;
 	uint8_t *last_alloc;
 	uint8_t *second_to_last_alloc;
 	size_t free_offset;
 };
 
-#define MEM_POOL_INIT(buf_, size_)		\
+#define MEM_POOL_INIT(buf_, size_, alignment_)	\
 	{					\
 		.buf = (buf_),			\
 		.size = (size_),		\
+		.alignment = (alignment_),	\
 		.last_alloc = NULL,		\
 		.second_to_last_alloc = NULL,	\
 		.free_offset = 0,		\
@@ -46,10 +47,15 @@ static inline void mem_pool_reset(struct mem_pool *mp)
 }
 
 /* Initialize a memory pool. */
-static inline void mem_pool_init(struct mem_pool *mp, void *buf, size_t sz)
+static inline void mem_pool_init(struct mem_pool *mp, void *buf, size_t sz,
+					 size_t alignment)
 {
+	assert(alignment);
+	assert((uintptr_t)buf % alignment == 0);
+
 	mp->buf = buf;
 	mp->size = sz;
+	mp->alignment = alignment;
 	mem_pool_reset(mp);
 }
 

src/commonlib/mem_pool.c

@@ -7,8 +7,11 @@ void *mem_pool_alloc(struct mem_pool *mp, size_t sz)
 {
 	void *p;
 
-	/* Make all allocations be at least 8 byte aligned. */
+	if (mp->alignment == 0)
-	sz = ALIGN_UP(sz, 8);
+		return NULL;
+
+	/* We assume that mp->buf started mp->alignment aligned */
+	sz = ALIGN_UP(sz, mp->alignment);
 
 	/* Determine if any space available. */
 	if ((mp->size - mp->free_offset) < sz)

src/lib/cbfs.c

@@ -19,16 +19,17 @@
 #include <timestamp.h>
 
 #if ENV_STAGE_HAS_DATA_SECTION
-struct mem_pool cbfs_cache = MEM_POOL_INIT(_cbfs_cache, REGION_SIZE(cbfs_cache));
+struct mem_pool cbfs_cache =
+	MEM_POOL_INIT(_cbfs_cache, REGION_SIZE(cbfs_cache), sizeof(uint64_t));
 #else
-struct mem_pool cbfs_cache = MEM_POOL_INIT(NULL, 0);
+struct mem_pool cbfs_cache = MEM_POOL_INIT(NULL, 0, 0);
 #endif
 
 static void switch_to_postram_cache(int unused)
 {
 	if (_preram_cbfs_cache != _postram_cbfs_cache)
-		mem_pool_init(&cbfs_cache, _postram_cbfs_cache,
+		mem_pool_init(&cbfs_cache, _postram_cbfs_cache, REGION_SIZE(postram_cbfs_cache),
-			      REGION_SIZE(postram_cbfs_cache));
+			      sizeof(uint64_t));
 }
 ROMSTAGE_CBMEM_INIT_HOOK(switch_to_postram_cache);