soc/intel/common/mrc_cache: Honor MRC data as a constant pointer

The MRC cache API has absolutely no reason to modify the data it is
asked to stash. Reflect that by taking all "data" parameters as
const void *.

Change-Id: I7a14ffd7d5726aa9aa5db81df82c06e7f87b9d9f
Signed-off-by: Alexandru Gagniuc <alexandrux.gagniuc@intel.com>
Reviewed-on: https://review.coreboot.org/14250
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Leroy P Leahy <leroy.p.leahy@intel.com>

src/drivers/intel/fsp1_1/romstage.c

@@ -372,7 +372,7 @@ __attribute__((weak)) int mrc_cache_get_current(
 }
 
 /* Save the memory configuration data */
-__attribute__((weak)) int mrc_cache_stash_data(void *data, size_t size)
+__attribute__((weak)) int mrc_cache_stash_data(const void *data, size_t size)
 {
 	printk(BIOS_DEBUG, "WEAK: %s/%s called\n", __FILE__, __func__);
 	return -1;

src/soc/intel/common/mrc_cache.c

@@ -162,7 +162,7 @@ int mrc_cache_get_current(const struct mrc_saved_data **cache)
 	return mrc_cache_get_current_with_version(cache, 0);
 }
 /* Fill in mrc_saved_data structure with payload. */
-static void mrc_cache_fill(struct mrc_saved_data *cache, void *data,
+static void mrc_cache_fill(struct mrc_saved_data *cache, const void *data,
                            size_t size, uint32_t version)
 {
 	cache->signature = MRC_DATA_SIGNATURE;
@@ -173,7 +173,7 @@ static void mrc_cache_fill(struct mrc_saved_data *cache, void *data,
 	                                      cache->size);
 }
 
-int mrc_cache_stash_data_with_version(void *data, size_t size,
+int mrc_cache_stash_data_with_version(const void *data, size_t size,
 					uint32_t version)
 {
 	int cbmem_size;
@@ -199,7 +199,7 @@ int mrc_cache_stash_data_with_version(void *data, size_t size,
 	return 0;
 }
 
-int mrc_cache_stash_data(void *data, size_t size)
+int mrc_cache_stash_data(const void *data, size_t size)
 {
 	return mrc_cache_stash_data_with_version(data, size, 0);
 }

src/soc/intel/common/mrc_cache.h

@@ -34,8 +34,8 @@ int mrc_cache_get_current_with_version(const struct mrc_saved_data **cache,
 					uint32_t version);
 
 /* Stash the resulting MRC data to be saved in non-volatile storage later. */
-int mrc_cache_stash_data(void *data, size_t size);
+int mrc_cache_stash_data(const void *data, size_t size);
-int mrc_cache_stash_data_with_version(void *data, size_t size,
+int mrc_cache_stash_data_with_version(const void *data, size_t size,
 					uint32_t version);
 
 #endif /* _COMMON_MRC_CACHE_H_ */