diff options
| -rw-r--r-- | include/ecc.h | 53 | ||||
| -rw-r--r-- | libflash/Makefile.inc | 2 | ||||
| -rw-r--r-- | libflash/ecc.c | 175 |
3 files changed, 229 insertions, 1 deletions
diff --git a/include/ecc.h b/include/ecc.h new file mode 100644 index 0000000..d5c30cb --- /dev/null +++ b/include/ecc.h @@ -0,0 +1,53 @@ +/* Copyright 2013-2014 IBM Corp. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or + * implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/* This is based on the hostboot ecc code */ + +#ifndef __ECC_H +#define __ECC_H + +#include <stdint.h> +#include <skiboot.h> + +/* Bit field identifiers for syndrome calculations. */ +enum eccbitfields +{ + GD = 0xff, //< Good, ECC matches. + UE = 0xfe, //< Uncorrectable. + E0 = 71, //< Error in ECC bit 0 + E1 = 70, //< Error in ECC bit 1 + E2 = 69, //< Error in ECC bit 2 + E3 = 68, //< Error in ECC bit 3 + E4 = 67, //< Error in ECC bit 4 + E5 = 66, //< Error in ECC bit 5 + E6 = 65, //< Error in ECC bit 6 + E7 = 64 //< Error in ECC bit 7 +}; + +extern uint8_t eccmemcpy(uint64_t *dst, uint64_t *src, uint32_t len); + +/* + * Calculate the size of a buffer if ECC is added + * + * We add 1 byte of ecc for every 8 bytes of data. So we need to round up to 8 + * bytes length and then add 1/8 + */ +#define ECC_SIZE(len) (ALIGN_UP((len), 8) >> 3) +#define ECC_BUFFER_SIZE(len) (ALIGN_UP((len), 8) + ECC_SIZE(len)) +#define ECC_BUFFER_SIZE_CHECK(len) ((len) % 9) +#define BUFFER_SIZE_MINUS_ECC(len) ((len) * 8 / 9) + +#endif diff --git a/libflash/Makefile.inc b/libflash/Makefile.inc index 35f96f7..0850b24 100644 --- a/libflash/Makefile.inc +++ b/libflash/Makefile.inc @@ -1,4 +1,4 @@ -LIBFLASH_SRCS = libflash.c libffs.c +LIBFLASH_SRCS = libflash.c libffs.c ecc.c LIBFLASH_OBJS = $(LIBFLASH_SRCS:%.c=%.o) SUBDIRS += libflash diff --git a/libflash/ecc.c b/libflash/ecc.c new file mode 100644 index 0000000..9293743 --- /dev/null +++ b/libflash/ecc.c @@ -0,0 +1,175 @@ +/* Copyright 2013-2014 IBM Corp. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or + * implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/* This is based on the hostboot ecc code */ + +#include <stdint.h> +#include <ecc.h> + +/* + * 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[] = { + 0x0000e8423c0f99ff, + 0x00e8423c0f99ff00, + 0xe8423c0f99ff0000, + 0x423c0f99ff0000e8, + 0x3c0f99ff0000e842, + 0x0f99ff0000e8423c, + 0x99ff0000e8423c0f, + 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 + * + * @data: The 8 byte data to generate ECC for. + * @return: The 1 byte ECC corresponding to the data. + */ +static uint8_t eccgenerate(uint64_t data) +{ + int i; + uint8_t result = 0; + + for (i = 0; i < 8; i++) + result |= __builtin_parityl(eccmatrix[i] & data) << i; + + return result; +} + +/** + * Verify the data and ECC match or indicate how they are wrong. + * + * @data: The data to check ECC on. + * @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. + */ +static uint8_t eccverify(uint64_t data, uint8_t ecc) +{ + return syndromematrix[eccgenerate(data) ^ ecc]; +} + +/** + * Copy data from an input buffer with ECC to an output buffer without ECC. + * Correct it along the way and check for errors. + * + * @dst: destination buffer without ECC + * @src: source buffer with ECC + * @len: number of bytes of data to copy (without ecc). + Must be 8 byte aligned. + * + * @return: eccBitfield or 0-64. + * + * @retval GD - Data is good. + * @retval UE - Data is uncorrectable. + * @retval all others - which bit was corrected. + */ +uint8_t eccmemcpy(uint64_t *dst, uint64_t *src, uint32_t len) +{ + uint64_t *data; + uint8_t *ecc; + uint32_t i; + uint8_t badbit; + + if (len & 0x7) { + /* TODO: we could probably handle this */ + prerror("ECC data length must be 8 byte aligned length:%i\n", + len); + return UE; + } + + /* Handle in chunks of 8 bytes, so adjust the length */ + len >>= 3; + + for (i = 0; i < len; i++) { + data = (uint64_t *)((uint8_t *)src + i*9); + ecc = (uint8_t *)data + 8; + + badbit = eccverify(*data, *ecc); + if (badbit == UE) { + prerror("ECC: uncorrectable error: %016lx %02x\n", + (long unsigned int)*data, *ecc); + return badbit; + } + *dst = *data; + if (badbit <= UE) + prlog(PR_INFO, "ECC: correctable error: %i\n", badbit); + if (badbit < 64) + *dst = *data ^ (1ul << (63 - badbit)); + dst++; + } + return GD; +} |