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/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/usr/pnor/ecc.C $ */
/* */
/* IBM CONFIDENTIAL */
/* */
/* COPYRIGHT International Business Machines Corp. 2013 */
/* */
/* p1 */
/* */
/* Object Code Only (OCO) source materials */
/* Licensed Internal Code Source Materials */
/* IBM HostBoot Licensed Internal Code */
/* */
/* The source code for this program is not published or otherwise */
/* divested of its trade secrets, irrespective of what has been */
/* deposited with the U.S. Copyright Office. */
/* */
/* Origin: 30 */
/* */
/* IBM_PROLOG_END_TAG */
#include <stdio.h>
#include <endian.h>
#include <assert.h>
#include <pnor/ecc.H>
namespace PNOR
{
namespace ECC
{
/** Matrix used for ECC calculation.
*
* Each row of this is the set of data word bits that are used for
* the calculation of the corresponding ECC bit. The parity of the
* bitset is the value of the ECC bit.
*
* ie. ECC[n] = eccMatrix[n] & data
*
* Note: To make the math easier (and less shifts in resulting code),
* row0 = ECC7. HW numbering is MSB, order here is LSB.
*
* These values come from the HW design of the ECC algorithm.
*/
static uint64_t eccMatrix[] = {
//0000000000000000111010000100001000111100000011111001100111111111
0x0000e8423c0f99ff,
//0000000011101000010000100011110000001111100110011111111100000000
0x00e8423c0f99ff00,
//1110100001000010001111000000111110011001111111110000000000000000
0xe8423c0f99ff0000,
//0100001000111100000011111001100111111111000000000000000011101000
0x423c0f99ff0000e8,
//0011110000001111100110011111111100000000000000001110100001000010
0x3c0f99ff0000e842,
//0000111110011001111111110000000000000000111010000100001000111100
0x0f99ff0000e8423c,
//1001100111111111000000000000000011101000010000100011110000001111
0x99ff0000e8423c0f,
//1111111100000000000000001110100001000010001111000000111110011001
0xff0000e8423c0f99
};
/** Syndrome calculation matrix.
*
* Maps syndrome to flipped bit.
*
* To perform ECC correction, this matrix is a look-up of the bit
* that is bad based on the binary difference of the good and bad
* ECC. This difference is called the "syndrome".
*
* When a particular bit is on in the data, it cause a column from
* eccMatrix being XOR'd into the ECC field. This column is the
* "effect" of each bit. If a bit is flipped in the data then its
* "effect" is missing from the ECC. You can calculate ECC on unknown
* quality data and compare the ECC field between the calculated
* value and the stored value. If the difference is zero, then the
* data is clean. If the difference is non-zero, you look up the
* difference in the syndrome table to identify the "effect" that
* is missing, which is the bit that is flipped.
*
* Notice that ECC bit flips are recorded by a single "effect"
* bit (ie. 0x1, 0x2, 0x4, 0x8 ...) and double bit flips are identified
* by the UE status in the table.
*
* Bits are in MSB order.
*/
static uint8_t syndromeMatrix[] = {
GD, E7, E6, UE, E5, UE, UE, 47, E4, UE, UE, 37, UE, 35, 39, UE,
E3, UE, UE, 48, UE, 30, 29, UE, UE, 57, 27, UE, 31, UE, UE, UE,
E2, UE, UE, 17, UE, 18, 40, UE, UE, 58, 22, UE, 21, UE, UE, UE,
UE, 16, 49, UE, 19, UE, UE, UE, 23, UE, UE, UE, UE, 20, UE, UE,
E1, UE, UE, 51, UE, 46, 9, UE, UE, 34, 10, UE, 32, UE, UE, 36,
UE, 62, 50, UE, 14, UE, UE, UE, 13, UE, UE, UE, UE, UE, UE, UE,
UE, 61, 8, UE, 41, UE, UE, UE, 11, UE, UE, UE, UE, UE, UE, UE,
15, UE, UE, UE, UE, UE, UE, UE, UE, UE, 12, UE, UE, UE, UE, UE,
E0, UE, UE, 55, UE, 45, 43, UE, UE, 56, 38, UE, 1, UE, UE, UE,
UE, 25, 26, UE, 2, UE, UE, UE, 24, UE, UE, UE, UE, UE, 28, UE,
UE, 59, 54, UE, 42, UE, UE, 44, 6, UE, UE, UE, UE, UE, UE, UE,
5, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE,
UE, 63, 53, UE, 0, UE, UE, UE, 33, UE, UE, UE, UE, UE, UE, UE,
3, UE, UE, 52, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE,
7, UE, UE, UE, UE, UE, UE, UE, UE, 60, UE, UE, UE, UE, UE, UE,
UE, UE, UE, UE, 4, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE,
};
/** Create the ECC field corresponding to a 8-byte data field
*
* @param[in] i_data - The 8 byte data to generate ECC for.
* @return The 1 byte ECC corresponding to the data.
*/
uint8_t generateECC(uint64_t i_data)
{
uint8_t result = 0;
for (int i = 0; i < 8; i++)
{
result |= __builtin_parityl(eccMatrix[i] & i_data) << i;
}
return result;
}
/** Verify the data and ECC match or indicate how they are wrong.
*
* @param[in] i_data - The data to check ECC on.
* @param[in] i_ecc - The [supposed] ECC for the data.
*
* @return eccBitfield or 0-64.
*
* @retval GD - Indicates the data is good (matches ECC).
* @retval UE - Indicates the data is uncorrectable.
* @retval all others - Indication of which bit is incorrect.
*/
uint8_t verifyECC(uint64_t i_data, uint8_t i_ecc)
{
return syndromeMatrix[generateECC(i_data) ^ i_ecc];
}
/** Correct the data and/or ECC.
*
* @param[in,out] io_data - Data to check / correct.
* @param[in,out] io_ecc - ECC to check / correct.
*
* @return eccBitfield or 0-64.
*
* @retval GD - Data is good.
* @retval UE - Data is uncorrectable.
* @retval all others - which bit was corrected.
*/
uint8_t correctECC(uint64_t& io_data, uint8_t& io_ecc)
{
uint8_t badBit = verifyECC(io_data, io_ecc);
if ((badBit != GD) && (badBit != UE)) // Good is done, UE is hopeless.
{
// Determine if the ECC or data part is bad, do bit flip.
if (badBit >= E7)
{
io_ecc ^= (1 << (badBit - E7));
}
else
{
io_data ^= (1ul << (63 - badBit));
}
}
return badBit;
}
void injectECC(const uint8_t* i_src, size_t i_srcSz,
uint8_t* o_dst)
{
assert(0 == (i_srcSz % sizeof(uint64_t)));
for(size_t i = 0, o = 0;
i < i_srcSz;
i += sizeof(uint64_t), o += sizeof(uint64_t) + sizeof(uint8_t))
{
// Read data word, copy to destination.
uint64_t data = *reinterpret_cast<const uint64_t*>(&i_src[i]);
*reinterpret_cast<uint64_t*>(&o_dst[o]) = data;
data = be64toh(data);
// Calculate ECC, copy to destination.
uint8_t ecc = generateECC(data);
o_dst[o + sizeof(uint64_t)] = ecc;
}
}
eccStatus removeECC(uint8_t* io_src,
uint8_t* o_dst, size_t i_dstSz)
{
assert(0 == (i_dstSz % sizeof(uint64_t)));
eccStatus rc = CLEAN;
for(size_t i = 0, o = 0;
o < i_dstSz;
i += sizeof(uint64_t) + sizeof(uint8_t), o += sizeof(uint64_t))
{
// Read data and ECC parts.
uint64_t data = *reinterpret_cast<uint64_t*>(&io_src[i]);
data = be64toh(data);
uint8_t ecc = io_src[i + sizeof(uint64_t)];
// Calculate failing bit and fix data.
uint8_t badBit = correctECC(data, ecc);
// Return data to big endian.
data = htobe64(data);
// Perform correction and status update.
if (badBit == UE)
{
rc = UNCORRECTABLE;
}
else if (badBit != GD)
{
if (rc != UNCORRECTABLE)
{
rc = CORRECTED;
}
*reinterpret_cast<uint64_t*>(&io_src[i]) = data;
io_src[i + sizeof(uint64_t)] = ecc;
}
// Copy fixed data to destination buffer.
*reinterpret_cast<uint64_t*>(&o_dst[o]) = data;
}
return rc;
}
}
}
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