82802ab: touch only blocks that need updating

Flash pages, which where excluded from updating using the exclude or the
layout option, as well as areas, whose flash contents already contain
the desired data, will be skipped. These ensures absolute data security
of critical areas (BIOS boot block), e.g. against a sudden power off or
a CPU hangup during flashing. As a nice side effect, it speeds up the
flash process, if the BIOS to be flashed is very similar to the version
in flash.

Corresponding to flashrom svn r217 and coreboot v2 svn r3260.
Signed-off-by: Claus Gindhart <claus.gindhart@kontron.com>
Acked-by: Stefan Reinauer <stepan@coresystems.de>

82802ab.c

@@ -27,6 +27,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <stdint.h>
 #include "flash.h"
 
@@ -110,6 +111,7 @@ int erase_82802ab_block(struct flashchip *flash, int offset)
 {
 	volatile uint8_t *bios = flash->virtual_memory + offset;
 	volatile uint8_t *wrprotect = flash->virtual_registers + offset + 2;
+	int j;
 	uint8_t status;
 
 	// clear status register
@@ -128,6 +130,12 @@ int erase_82802ab_block(struct flashchip *flash, int offset)
 	// now let's see what the register is
 	status = wait_82802ab(flash->virtual_memory);
 	//print_82802ab_status(status);
+	for (j = 0; j < flash->page_size; j++) {
+		if (*(bios + j) != 0xFF) {
+			printf("BLOCK ERASE failed at 0x%x\n", offset);
+			return -1;
+		}
+	}
 	printf("DONE BLOCK 0x%x\n", offset);
 
 	return 0;
@@ -167,17 +175,29 @@ int write_82802ab(struct flashchip *flash, uint8_t *buf)
 	int page_size = flash->page_size;
 	volatile uint8_t *bios = flash->virtual_memory;
 
-	erase_82802ab(flash);
-	if (*bios != 0xff) {
-		printf("ERASE FAILED\n");
-		return -1;
-	}
-	printf("Programming page: ");
+	printf("Programming page: \n");
 	for (i = 0; i < total_size / page_size; i++) {
+		printf
+		    ("\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b");
 		printf("%04d at address: 0x%08x", i, i * page_size);
+
+		/* Auto Skip Blocks, which already contain the desired data
+		 * Faster, because we only write, what has changed
+		 * More secure, because blocks, which are excluded
+		 * (with the exclude or layout feature)
+		 * or not erased and rewritten; their data is retained also in
+		 * sudden power off situations
+		 */
+		if (!memcmp((void *)(buf + i * page_size),
+			    (void *)(bios + i * page_size), page_size)) {
+			printf("SKIPPED\n");
+			continue;
+		}
+
+		/* erase block by block and write block by block; this is the most secure way */
+		erase_82802ab_block(flash, i * page_size);
 		write_page_82802ab(bios, buf + i * page_size,
 				   bios + i * page_size, page_size);
-		printf("\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b");
 	}
 	printf("\n");
 	protect_jedec(bios);