diff options
Diffstat (limited to 'drivers/mtd/nand/gpmi-nand/gpmi-lib.c')
| -rw-r--r-- | drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c index 87e658ce23ef..27f272ed502a 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c @@ -1353,3 +1353,156 @@ int gpmi_read_page(struct gpmi_nand_data *this, set_dma_type(this, DMA_FOR_READ_ECC_PAGE); return start_dma_with_bch_irq(this, desc); } + +/** + * gpmi_copy_bits - copy bits from one memory region to another + * @dst: destination buffer + * @dst_bit_off: bit offset we're starting to write at + * @src: source buffer + * @src_bit_off: bit offset we're starting to read from + * @nbits: number of bits to copy + * + * This functions copies bits from one memory region to another, and is used by + * the GPMI driver to copy ECC sections which are not guaranteed to be byte + * aligned. + * + * src and dst should not overlap. + * + */ +void gpmi_copy_bits(u8 *dst, size_t dst_bit_off, + const u8 *src, size_t src_bit_off, + size_t nbits) +{ + size_t i; + size_t nbytes; + u32 src_buffer = 0; + size_t bits_in_src_buffer = 0; + + if (!nbits) + return; + + /* + * Move src and dst pointers to the closest byte pointer and store bit + * offsets within a byte. + */ + src += src_bit_off / 8; + src_bit_off %= 8; + + dst += dst_bit_off / 8; + dst_bit_off %= 8; + + /* + * Initialize the src_buffer value with bits available in the first + * byte of data so that we end up with a byte aligned src pointer. + */ + if (src_bit_off) { + src_buffer = src[0] >> src_bit_off; + if (nbits >= (8 - src_bit_off)) { + bits_in_src_buffer += 8 - src_bit_off; + } else { + src_buffer &= GENMASK(nbits - 1, 0); + bits_in_src_buffer += nbits; + } + nbits -= bits_in_src_buffer; + src++; + } + + /* Calculate the number of bytes that can be copied from src to dst. */ + nbytes = nbits / 8; + + /* Try to align dst to a byte boundary. */ + if (dst_bit_off) { + if (bits_in_src_buffer < (8 - dst_bit_off) && nbytes) { + src_buffer |= src[0] << bits_in_src_buffer; + bits_in_src_buffer += 8; + src++; + nbytes--; + } + + if (bits_in_src_buffer >= (8 - dst_bit_off)) { + dst[0] &= GENMASK(dst_bit_off - 1, 0); + dst[0] |= src_buffer << dst_bit_off; + src_buffer >>= (8 - dst_bit_off); + bits_in_src_buffer -= (8 - dst_bit_off); + dst_bit_off = 0; + dst++; + if (bits_in_src_buffer > 7) { + bits_in_src_buffer -= 8; + dst[0] = src_buffer; + dst++; + src_buffer >>= 8; + } + } + } + + if (!bits_in_src_buffer && !dst_bit_off) { + /* + * Both src and dst pointers are byte aligned, thus we can + * just use the optimized memcpy function. + */ + if (nbytes) + memcpy(dst, src, nbytes); + } else { + /* + * src buffer is not byte aligned, hence we have to copy each + * src byte to the src_buffer variable before extracting a byte + * to store in dst. + */ + for (i = 0; i < nbytes; i++) { + src_buffer |= src[i] << bits_in_src_buffer; + dst[i] = src_buffer; + src_buffer >>= 8; + } + } + /* Update dst and src pointers */ + dst += nbytes; + src += nbytes; + + /* + * nbits is the number of remaining bits. It should not exceed 8 as + * we've already copied as much bytes as possible. + */ + nbits %= 8; + + /* + * If there's no more bits to copy to the destination and src buffer + * was already byte aligned, then we're done. + */ + if (!nbits && !bits_in_src_buffer) + return; + + /* Copy the remaining bits to src_buffer */ + if (nbits) + src_buffer |= (*src & GENMASK(nbits - 1, 0)) << + bits_in_src_buffer; + bits_in_src_buffer += nbits; + + /* + * In case there were not enough bits to get a byte aligned dst buffer + * prepare the src_buffer variable to match the dst organization (shift + * src_buffer by dst_bit_off and retrieve the least significant bits + * from dst). + */ + if (dst_bit_off) + src_buffer = (src_buffer << dst_bit_off) | + (*dst & GENMASK(dst_bit_off - 1, 0)); + bits_in_src_buffer += dst_bit_off; + + /* + * Keep most significant bits from dst if we end up with an unaligned + * number of bits. + */ + nbytes = bits_in_src_buffer / 8; + if (bits_in_src_buffer % 8) { + src_buffer |= (dst[nbytes] & + GENMASK(7, bits_in_src_buffer % 8)) << + (nbytes * 8); + nbytes++; + } + + /* Copy the remaining bytes to dst */ + for (i = 0; i < nbytes; i++) { + dst[i] = src_buffer; + src_buffer >>= 8; + } +} |