[flashrom] [PATCH] Add a write granularity of 512 bytes

[Mark Marshall]

I think this is needed for SPI Flash that has a page size of 512.

I have also changed the loop condition in a few places.  If the
length is not a multiple of stride we need to round up the result
of the divide.  (Either we need to round up the divide or we should
replace the lines "limit = min(stride, len - i * stride);" with
"limit = stride;".  Rounding up the result of the divide seems
to be the correct thing to do.).

Signed-off-by: Mark Marshall <mark.marshall at omicron.at>
---
 flash.h    |    2 ++
 flashrom.c |   38 +++++++++++++++++++++++++++++---------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/flash.h b/flash.h
index 0181798..876fdfd 100644
--- a/flash.h
+++ b/flash.h
@@ -66,11 +66,13 @@ enum chipbustype {
  * - 128 bytes: If less than 128 bytes are written, the rest will be
erased. Each write to a 128-byte region
  *   will trigger an automatic erase before anything is written. Very
uncommon behaviour.
  * - 256 bytes: If less than 256 bytes are written, the contents of
the unwritten bytes are undefined.
+ * - 512 bytes: If less than 512 bytes are written, the contents of
the unwritten bytes are undefined.
  */
 enum write_granularity {
 	write_gran_256bytes = 0, /* We assume 256 byte granularity by default. */
 	write_gran_1bit,
 	write_gran_1byte,
+	write_gran_512bytes,
 };

 /*
diff --git a/flashrom.c b/flashrom.c
index b682923..8413a4b 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -706,6 +706,13 @@ int need_erase(const uint8_t *have, const uint8_t
*want, unsigned int len, enum
 {
 	int result = 0;
 	unsigned int i, j, limit;
+	static uint8_t all_ffs[512];
+	static int all_ffs_init = 0;
+
+	if (!all_ffs_init) {
+		memset(all_ffs, 0xff, sizeof(all_ffs));
+		all_ffs_init = 1;
+	}

 	switch (gran) {
 	case write_gran_1bit:
@@ -723,21 +730,31 @@ int need_erase(const uint8_t *have, const
uint8_t *want, unsigned int len, enum
 			}
 		break;
 	case write_gran_256bytes:
-		for (j = 0; j < len / 256; j++) {
+		for (j = 0; j < (len + 255) / 256; j++) {
 			limit = min (256, len - j * 256);
 			/* Are 'have' and 'want' identical? */
 			if (!memcmp(have + j * 256, want + j * 256, limit))
 				continue;
-			/* have needs to be in erased state. */
-			for (i = 0; i < limit; i++)
-				if (have[j * 256 + i] != 0xff) {
-					result = 1;
-					break;
-				}
-			if (result)
+			/* 'have' needs to be in erased state. */
+			if (memcmp(have + j * 256, all_ffs, limit)) {
+				result = 1;
 				break;
+			}
 		}
 		break;
+	case write_gran_512bytes:
+		for (j = 0; j < (len + 511) / 512; j++) {
+			limit = min (512, len - j * 512);
+			/* Are 'have' and 'want' identical? */
+			if (!memcmp(have + j * 512, want + j * 512, limit))
+				continue;
+			/* 'have' needs to be in erased state. */
+			if (memcmp(have + j * 512, all_ffs, limit)) {
+				result = 1;
+				break;
+			}
+ 		}
+ 		break;
 	default:
 		msg_cerr("%s: Unsupported granularity! Please report a bug at "
 			 "flashrom at flashrom.org\n", __func__);
@@ -784,6 +801,9 @@ static unsigned int get_next_write(const uint8_t
*have, const uint8_t *want, uns
 	case write_gran_256bytes:
 		stride = 256;
 		break;
+	case write_gran_512bytes:
+		stride = 512;
+		break;
 	default:
 		msg_cerr("%s: Unsupported granularity! Please report a bug at "
 			 "flashrom at flashrom.org\n", __func__);
@@ -792,7 +812,7 @@ static unsigned int get_next_write(const uint8_t
*have, const uint8_t *want, uns
 		 */
 		return 0;
 	}
-	for (i = 0; i < len / stride; i++) {
+	for (i = 0; i < (len + stride - 1) / stride; i++) {
 		limit = min(stride, len - i * stride);
 		/* Are 'have' and 'want' identical? */
 		if (memcmp(have + i * stride, want + i * stride, limit)) {