Hello Everyone,
I believe, there is a bug in the mmc driver code pertaining to how u-boot detects memory size of an mmc device. However, I am not 100% sure, my solution conforms to the JEDEC standard. So I am putting it up for discussion.
Previously, sector count indicated by mmc devices in the EXT_CSD would only be used in u-boot if the size indicated is greater than 2 GB. This seems to be incorrect. I am working with a 4 GB Micron eMMC device that after partition configuration and setting the user data area to enhanced mode has a remaining capacity of less than 2 GB for the user data area. JESD84-B50 explicitly states in 6.2.4 that for these devices SEC_CNT from the EXT_CSD is still valid even if the memory size for that device has dropped below 2 GB by the partition configuration applied. The access mode bits from the OCR register seem to provide a better way to decide whether to use the CSD-based C_SIZE & C_MULT or the EXT_CSD-based SEC_CNT information when determining the device's capacity.
In particular, this fixes a bug where u-boot SPL would assign 0 to mmc->block_dev.lba later on in the mmc_startup() function and subsequently fail to load u-boot from that mmc due to the original C_SIZE & C_MULT code assigning a 4 TB size to mmc->capacity, that incorrect capacity never being overwritten by the SEC_CNT capacity calculation (due to its size being less than 2 GB) and then finally lldiv(mmc->capacity, mmc->read_bl_len) exceeding the 32-bit result data type of mmc->block_dev.lba.
Signed-off-by: Frank Bormann fbormann@yahoo.com --- drivers/mmc/mmc.c | 10 +++++----- include/mmc.h | 1 + 2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index c6a1c23..c5d1efc 100644 --- a/drivers/mmc/mmc.c +++ b/drivers/mmc/mmc.c @@ -935,19 +935,19 @@ static int mmc_startup(struct mmc *mmc) if (!IS_SD(mmc) && (mmc->version >= MMC_VERSION_4)) { /* check ext_csd version and capacity */ err = mmc_send_ext_csd(mmc, ext_csd); - if (!err && (ext_csd[EXT_CSD_REV] >= 2)) { + if (!err && (ext_csd[EXT_CSD_REV] >= 2) && + (mmc->ocr & OCR_ACCESS_MODE) == OCR_ACCESS_BY_SECTOR) { /* * According to the JEDEC Standard, the value of - * ext_csd's capacity is valid if the value is more - * than 2GB + * ext_csd's capacity is valid if the device addresses + * its memory by sector */ capacity = ext_csd[EXT_CSD_SEC_CNT] << 0 | ext_csd[EXT_CSD_SEC_CNT + 1] << 8 | ext_csd[EXT_CSD_SEC_CNT + 2] << 16 | ext_csd[EXT_CSD_SEC_CNT + 3] << 24; capacity *= MMC_MAX_BLOCK_LEN; - if ((capacity >> 20) > 2 * 1024) - mmc->capacity_user = capacity; + mmc->capacity_user = capacity; }
switch (ext_csd[EXT_CSD_REV]) { diff --git a/include/mmc.h b/include/mmc.h index e1060b9..816b580 100644 --- a/include/mmc.h +++ b/include/mmc.h @@ -104,6 +104,7 @@ #define OCR_HCS 0x40000000 #define OCR_VOLTAGE_MASK 0x007FFF80 #define OCR_ACCESS_MODE 0x60000000 +#define OCR_ACCESS_BY_SECTOR (1 << 30)
#define SECURE_ERASE 0x80000000