device/dram/ddr3: Move CRC calculation in a separate function
Calculating the CRC of a SPD may be useful by itself, so split that
part of the code in a separate function.
Change-Id: I6c20d3db380551865126fd890e89de6b06359207
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/4537
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
diff --git a/src/device/dram/ddr3.c b/src/device/dram/ddr3.c
index d98de91..9b4f490 100644
--- a/src/device/dram/ddr3.c
+++ b/src/device/dram/ddr3.c
@@ -49,6 +49,46 @@
}
/**
+ * \brief Calculate the CRC of a DDR3 SPD
+ *
+ * @param spd pointer to raw SPD data
+ * @param len length of data in SPD
+ *
+ * @return the CRC of the SPD data, or 0 when spd data is truncated.
+ */
+u16 spd_ddr3_calc_crc(u8 *spd, int len)
+{
+ int n_crc, i;
+ u8 *ptr;
+ u16 crc;
+
+ /* Find the number of bytes covered by CRC */
+ if (spd[0] & 0x80) {
+ n_crc = 117;
+ } else {
+ n_crc = 126;
+ }
+
+ if (len < n_crc)
+ /* Not enough bytes available to get the CRC */
+ return 0;
+
+ /* Compute the CRC */
+ crc = 0;
+ ptr = spd;
+ while (--n_crc >= 0) {
+ crc = crc ^ (int)*ptr++ << 8;
+ for (i = 0; i < 8; ++i)
+ if (crc & 0x8000) {
+ crc = crc << 1 ^ 0x1021;
+ } else {
+ crc = crc << 1;
+ }
+ }
+ return crc;
+}
+
+/**
* \brief Decode the raw SPD data
*
* Decodes a raw SPD data from a DDR3 DIMM, and organizes it into a
@@ -68,9 +108,8 @@
*/
int spd_decode_ddr3(dimm_attr * dimm, spd_raw_data spd)
{
- int nCRC, i, ret;
+ int ret;
u16 crc, spd_crc;
- u8 *ptr = spd;
u8 ftb_divisor, ftb_dividend, capacity_shift, bus_width, sdram_width;
u8 reg8;
u32 mtb; /* medium time base */
@@ -88,24 +127,7 @@
}
dimm->dram_type = SPD_MEMORY_TYPE_SDRAM_DDR3;
- /* Find the number of bytes covered by CRC */
- if (spd[0] & 0x80) {
- nCRC = 117;
- } else {
- nCRC = 126;
- }
-
- /* Compute the CRC */
- crc = 0;
- while (--nCRC >= 0) {
- crc = crc ^ (int)*ptr++ << 8;
- for (i = 0; i < 8; ++i)
- if (crc & 0x8000) {
- crc = crc << 1 ^ 0x1021;
- } else {
- crc = crc << 1;
- }
- }
+ crc = spd_ddr3_calc_crc(spd, sizeof(spd));
/* Compare with the CRC in the SPD */
spd_crc = (spd[127] << 8) + spd[126];
/* Verify the CRC is correct */