On 25/02/15 23:55, Al Cooper 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 <[email protected]>
> ---
> 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;
> }
>
This has been covered before:
http://marc.info/?l=linux-mmc&m=138736492823089&w=2
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