[v1] spl: nand: allow partial nand page reads during nand_spl_load_image

[Colin Foster]

The nand_spl_load_image function was guaranteed to read an entire block
into RAM, regardless of how many bytes were to be read. This is
particularly problematic when spl_load_legacy_image is called, as this
function attempts to load a struct image_header but gets surprised with
a full flash sector.

Allow partial reads to restore functionality to the code path
spl_nand_load_element() -> spl_load_legacy_img() ->
spl_nand_legacy_read(load, header, sizeof(hdr), header);

Signed-off-by: Colin Foster <colin.foster at in-advantage.com>
---
 drivers/mtd/nand/raw/nand_spl_loaders.c | 36 ++++++++++++++++---------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_spl_loaders.c b/drivers/mtd/nand/raw/nand_spl_loaders.c
index 4befc75c04..84ac482c06 100644
--- a/drivers/mtd/nand/raw/nand_spl_loaders.c
+++ b/drivers/mtd/nand/raw/nand_spl_loaders.c
@@ -1,9 +1,18 @@
+/*
+ * Temporary storage for non NAND page aligned and non NAND page sized
+ * reads. Note: This does not support runtime detected FLASH yet, but
+ * that should be reasonably easy to fix by making the buffer large
+ * enough :)
+ */
+static u8 scratch_buf[CONFIG_SYS_NAND_PAGE_SIZE];
+
 int nand_spl_load_image(uint32_t offs, unsigned int size, void *dst)
 {
+	unsigned int read_this_time = CONFIG_SYS_NAND_PAGE_SIZE;
+	unsigned int size_remaining = size;
 	unsigned int block, lastblock;
 	unsigned int page, page_offset;
 
-	/* offs has to be aligned to a page address! */
 	block = offs / CONFIG_SYS_NAND_BLOCK_SIZE;
 	lastblock = (offs + size - 1) / CONFIG_SYS_NAND_BLOCK_SIZE;
 	page = (offs % CONFIG_SYS_NAND_BLOCK_SIZE) / CONFIG_SYS_NAND_PAGE_SIZE;
@@ -12,8 +21,18 @@ int nand_spl_load_image(uint32_t offs, unsigned int size, void *dst)
 	while (block <= lastblock) {
 		if (!nand_is_bad_block(block)) {
 			/* Skip bad blocks */
-			while (page < CONFIG_SYS_NAND_PAGE_COUNT) {
-				nand_read_page(block, page, dst);
+			while (page < CONFIG_SYS_NAND_PAGE_COUNT &&
+			       size_remaining > 0) {
+				if (size_remaining < CONFIG_SYS_NAND_PAGE_SIZE)
+				{
+					nand_read_page(block, page,
+						       scratch_buf);
+					memcpy(dst, scratch_buf,
+					       size_remaining);
+					read_this_time = size_remaining;
+				} else {
+					nand_read_page(block, page, dst);
+				}
 				/*
 				 * When offs is not aligned to page address the
 				 * extra offset is copied to dst as well. Copy
@@ -26,7 +45,8 @@ int nand_spl_load_image(uint32_t offs, unsigned int size, void *dst)
 					dst = (void *)((int)dst - page_offset);
 					page_offset = 0;
 				}
-				dst += CONFIG_SYS_NAND_PAGE_SIZE;
+				dst += read_this_time;
+				size_remaining -= read_this_time;
 				page++;
 			}
 
@@ -70,14 +90,6 @@ u32 nand_spl_adjust_offset(u32 sector, u32 offs)
 }
 
 #ifdef CONFIG_SPL_UBI
-/*
- * Temporary storage for non NAND page aligned and non NAND page sized
- * reads. Note: This does not support runtime detected FLASH yet, but
- * that should be reasonably easy to fix by making the buffer large
- * enough :)
- */
-static u8 scratch_buf[CONFIG_SYS_NAND_PAGE_SIZE];
-
 /**
  * nand_spl_read_block - Read data from physical eraseblock into a buffer
  * @block:	Number of the physical eraseblock
-- 
2.25.1