I understand. For an API that accepts sectors that are not erase block aligned the correct answer really is 1 sector for this eMMC/Host controller combination. Unfortunately this hangs mkfs.ext4 for about 10 hours. Have there been any other suggested solutions? On Wed, Feb 25, 2015 at 4:55 PM, Al Cooper <alcooperx@xxxxxxxxx> wrote: > mkfs.ext4 will erase the entire partition on the eMMC device before > writing the actual filesystem. The number of blocks erased on each > erase eMMC command is determined at run time based on the max erase > or trim time specified by the EXT_CSD in the eMMC device and the max eMMC > command timeout supported by the host controller. The routine in the > kernel that calculates the max number of blocks specified per command > returns 1 with some combinations of host controllers with a short max > command timeout and eMMC devices with long max erase or trim time. > This will end up requiring over 8 million erase sequences on a 4GB > eMMC partition and will take many hours. > > For example, on a host controller with a 50MHz timeout clock > specified in the Host CAPS register and an eMMC device > with a TRIM Multiplier of 6 specified in the EXT_CSD we get > 2^27/50000000=2.68 secs for a max command timeout and 6*.300=1.8 secs > for a trim operation which only allows 1 per trim command. The problem > seems to be in mmc_do_calc_max_discard() which does it's calculations > based on erase blocks but converts to and returns write blocks > (2MB blocks to 512 bytes blocks for a typical eMMC device) unless > the value is 1 in which case it just returns the 1. The routine also > subtracts 1 from the max calculation before converting from erase to > write blocks which should not be needed. > > This change will convert all non-zero max calculations from erase > to write blocks and will no longer subtract 1 from the erase block > max before converting to write blocks. This allow mkfs.ext4 to run > in 30 secs instead of >10 hours. > > Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx> > --- > drivers/mmc/core/core.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > index 23f10f7..1b61ac0 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -2231,16 +2231,13 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card, > if (!qty) > return 0; > > - if (qty == 1) > - return 1; > - > /* Convert qty to sectors */ > if (card->erase_shift) > - max_discard = --qty << card->erase_shift; > + max_discard = qty << card->erase_shift; > else if (mmc_card_sd(card)) > max_discard = qty; > else > - max_discard = --qty * card->erase_size; > + max_discard = qty * card->erase_size; > > return max_discard; > } > -- > 1.9.0.138.g2de3478 > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
