[PATCH] lib: sparse: allocate blkcnt instead of arbitrary small number

[Mattijs Korpershoek]

Commit 62649165cb02 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned")
fixed cache alignment for systems with a D-CACHE.

However it introduced some performance regressions [1] on system
flashing huge images, such as Android.

On AM62x SK EVM, we also observe such performance penalty:
Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 23.954s]
Writing 'super'                                    OKAY [ 75.926s]
Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.641s]
Writing 'super'                                    OKAY [ 62.849s]
Finished. Total time: 182.474s

The reason for this is that we use an arbitrary small buffer
(info->blksz * 100) for transferring.

Fix it by using a bigger buffer (info->blksz * blkcnt) as suggested in
the original's patch review [2].

With this patch, performance impact is mitigated:
Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 24.006s]
Writing 'super'                                    OKAY [ 15.920s]
Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.651s]
Writing 'super'                                    OKAY [ 14.665s]
Finished. Total time: 74.346s

[1] https://lore.kernel.org/r/20221118121323.4009193-1-gary.bisson@boundarydevices.com
[2] https://lore.kernel.org/r/all/43e4c17c-4483-ec8e-f843-9b4c5569bd18@seco.com/

Fixes: 62649165cb02 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned")
Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
---
 lib/image-sparse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/image-sparse.c b/lib/image-sparse.c
index 5ec0f94ab3eb..25aed0604192 100644
--- a/lib/image-sparse.c
+++ b/lib/image-sparse.c
@@ -55,7 +55,7 @@ static lbaint_t write_sparse_chunk_raw(struct sparse_storage *info,
 				       void *data,
 				       char *response)
 {
-	lbaint_t n = blkcnt, write_blks, blks = 0, aligned_buf_blks = 100;
+	lbaint_t n = blkcnt, write_blks, blks = 0, aligned_buf_blks = blkcnt;
 	uint32_t *aligned_buf = NULL;
 
 	if (CONFIG_IS_ENABLED(SYS_DCACHE_OFF)) {

---
base-commit: 2f4664f5c3edc55b18d8906f256a4c8e303243c0
change-id: 20230616-sparse-flash-fix-9c2852aa8d16

Best regards,
-- 
Mattijs Korpershoek <mkorpershoek at baylibre.com>