[coreboot-gerrit] Change in ...coreboot[master]: util/amdfwutil: Clarify call to fletcher32

[Marshall Dawson (Code Review)]

Marshall Dawson has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/31728

Change subject: util/amdfwutil: Clarify call to fletcher32
......................................................................

util/amdfwutil: Clarify call to fletcher32

The fletcher32 algorighm generates a sum over a range of 16-bit
WORDs.  Change the function's interface to be more generic,
accepting a more intuitive size in BYTEs.  Don't require the
caller to understand the nature of the algorithm and convert to
WORDs prior to calling.

TEST=Verify no difference in amdfw.rom for google/grunt before and after

Change-Id: Iad70558347cbdb3c51bd598479ee4484219c0869
Signed-off-by: Marshall Dawson 
---
M util/amdfwtool/amdfwtool.c
1 file changed, 14 insertions(+), 9 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/28/31728/1

diff --git a/util/amdfwtool/amdfwtool.c b/util/amdfwtool/amdfwtool.c
index 3ed6885..e1c59ae 100644
--- a/util/amdfwtool/amdfwtool.c
+++ b/util/amdfwtool/amdfwtool.c
@@ -121,12 +121,15 @@
  *              inserted 8 bytes after the beginning of the file.
  *    stderr:   Used to print out error messages.
  */
-static uint32_t fletcher32(const uint16_t *pptr, int length)
+static uint32_t fletcher32(const void *data, int length)
 {
    uint32_t c0;
    uint32_t c1;
    uint32_t checksum;
    int index;
+	const uint16_t *pptr = data;
+
+	length /= 2;

c0 = 0xFFFF;
    c1 = 0xFFFF;
@@ -138,13 +141,15 @@
    	c0 += *(pptr++);
    	c1 += c0;
    	if ((index % 360) == 0) {
-			c0 = (c0 & 0xFFFF) + (c0 >> 16);	// Sum0 modulo 65535 + the overflow
-			c1 = (c1 & 0xFFFF) + (c1 >> 16);	// Sum1 modulo 65535 + the overflow
+			/* Sums[0,1] mod 64K + overflow */
+			c0 = (c0 & 0xFFFF) + (c0 >> 16);
+			c1 = (c1 & 0xFFFF) + (c1 >> 16);
    	}
    }

-	c0 = (c0 & 0xFFFF) + (c0 >> 16);	// Sum0 modulo 65535 + the overflow
-	c1 = (c1 & 0xFFFF) + (c1 >> 16);	// Sum1 modulo 65535 + the overflow
+	/* Sums[0,1] mod 64K + overflow */
+	c0 = (c0 & 0xFFFF) + (c0 >> 16);
+	c1 = (c1 & 0xFFFF) + (c1 >> 16);
    checksum = (c1 << 16) | c0;

return checksum;
@@ -331,9 +336,9 @@
    /* checksum everything that comes after the Checksum field */
    pspdir->header.checksum = fletcher32(
    				(void *)&pspdir->header.num_entries,
-					(count * sizeof(psp_directory_entry)
+					count * sizeof(psp_directory_entry)
    				+ sizeof(pspdir->header.num_entries)
-					+ sizeof(pspdir->header.reserved)) / 2);
+					+ sizeof(pspdir->header.reserved));
 }

static uint32_t integrate_firmwares(char *base, uint32_t pos,
@@ -848,11 +853,11 @@
    	combo_dir->header.reserved[1] = 0;
    	combo_dir->header.checksum = fletcher32(
    			(void *)&combo_dir->header.num_entries,
-				(1 * sizeof(psp_directory_entry)
+				1 * sizeof(psp_directory_entry)
    			+ sizeof(combo_dir->header.num_entries)
    			+ sizeof(combo_dir->header.lookup)
    			+ sizeof(combo_dir->header.reserved[0])
-				+ sizeof(combo_dir->header.reserved[1])) / 2);
+				+ sizeof(combo_dir->header.reserved[1]));
 #else
    	current = integrate_psp_firmwares(rom, current, psp2dir,
    			amd_psp2_fw_table, rom_size);