From: Stephen Warren <swarren@xxxxxxxxxx> In mmc_do_calc_max_discard(), if any value has been assigned to qty, that value must have passed the timeout checks in the loop. Hence, qty is the maximum number of erase blocks that fit within the timeout, not the first value that does not fit into the timeout. In turn, this means we don't need any special case for (qty == 1); any value of qty needs to be multiplied by the card's erase shift, and we don't need to decrement qty before doing so. Without this patch, on the NVIDIA Tegra Cardhu board, the loops result in qty == 1, which is immediately returned. This causes discard to operate a single sector at a time, which is chronically slow. With this patch in place, discard operates a single erase block at a time, which is reasonably fast. Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx> Cc: Dong Aisheng <dongas86@xxxxxxxxx> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx> Cc: Vladimir Zapolskiy <vz@xxxxxxxxx> Fixes: e056a1b5b67b "(mmc: queue: let host controllers specify maximum discard timeout") Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> --- If this makes sense, I wonder if it should be Cc: stable? --- 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 57a2b403bf8e..dd793cf4ef46 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -2150,16 +2150,13 @@ 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; } -- 1.8.1.5 -- 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
