diff options
| -rw-r--r-- | drivers/mtd/spi-nor/core.c | 76 |
1 files changed, 75 insertions, 1 deletions
diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c index ac4b960101cc..1b594f720b6c 100644 --- a/drivers/mtd/spi-nor/core.c +++ b/drivers/mtd/spi-nor/core.c @@ -2014,6 +2014,76 @@ static const struct flash_info *spi_nor_detect(struct spi_nor *nor) return info; } +/* + * On Octal DTR capable flashes, reads cannot start or end at an odd + * address in Octal DTR mode. Extra bytes need to be read at the start + * or end to make sure both the start address and length remain even. + */ +static int spi_nor_octal_dtr_read(struct spi_nor *nor, loff_t from, size_t len, + u_char *buf) +{ + u_char *tmp_buf; + size_t tmp_len; + loff_t start, end; + int ret, bytes_read; + + if (IS_ALIGNED(from, 2) && IS_ALIGNED(len, 2)) + return spi_nor_read_data(nor, from, len, buf); + else if (IS_ALIGNED(from, 2) && len > PAGE_SIZE) + return spi_nor_read_data(nor, from, round_down(len, PAGE_SIZE), + buf); + + tmp_buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!tmp_buf) + return -ENOMEM; + + start = round_down(from, 2); + end = round_up(from + len, 2); + + /* + * Avoid allocating too much memory. The requested read length might be + * quite large. Allocating a buffer just as large (slightly bigger, in + * fact) would put unnecessary memory pressure on the system. + * + * For example if the read is from 3 to 1M, then this will read from 2 + * to 4098. The reads from 4098 to 1M will then not need a temporary + * buffer so they can proceed as normal. + */ + tmp_len = min_t(size_t, end - start, PAGE_SIZE); + + ret = spi_nor_read_data(nor, start, tmp_len, tmp_buf); + if (ret == 0) { + ret = -EIO; + goto out; + } + if (ret < 0) + goto out; + + /* + * More bytes are read than actually requested, but that number can't be + * reported to the calling function or it will confuse its calculations. + * Calculate how many of the _requested_ bytes were read. + */ + bytes_read = ret; + + if (from != start) + ret -= from - start; + + /* + * Only account for extra bytes at the end if they were actually read. + * For example, if the total length was truncated because of temporary + * buffer size limit then the adjustment for the extra bytes at the end + * is not needed. + */ + if (start + bytes_read == end) + ret -= end - (from + len); + + memcpy(buf, tmp_buf + (from - start), ret); +out: + kfree(tmp_buf); + return ret; +} + static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) { @@ -2031,7 +2101,11 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, while (len) { loff_t addr = from; - ret = spi_nor_read_data(nor, addr, len, buf); + if (nor->read_proto == SNOR_PROTO_8_8_8_DTR) + ret = spi_nor_octal_dtr_read(nor, addr, len, buf); + else + ret = spi_nor_read_data(nor, addr, len, buf); + if (ret == 0) { /* We shouldn't see 0-length reads */ ret = -EIO; |