mmc: core: Optimize the mmc erase size alignment

In most cases the 'card->erase_size' is power of 2, then the round_up/down()
function is more efficient than '%' operation when the 'card->erase_size' is
power of 2.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Tested-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -2212,6 +2212,23 @@ static unsigned int mmc_align_erase_size(struct mmc_card *card,
 {
 	unsigned int from_new = *from, nr_new = nr, rem;
 
+	/*
+	 * When the 'card->erase_size' is power of 2, we can use round_up/down()
+	 * to align the erase size efficiently.
+	 */
+	if (is_power_of_2(card->erase_size)) {
+		unsigned int temp = from_new;
+
+		from_new = round_up(temp, card->erase_size);
+		rem = from_new - temp;
+
+		if (nr_new > rem)
+			nr_new -= rem;
+		else
+			return 0;
+
+		nr_new = round_down(nr_new, card->erase_size);
+	} else {
 		rem = from_new % card->erase_size;
 		if (rem) {
 			rem = card->erase_size - rem;
@@ -2225,6 +2242,7 @@ static unsigned int mmc_align_erase_size(struct mmc_card *card,
 		rem = nr_new % card->erase_size;
 		if (rem)
 			nr_new -= rem;
+	}
 
 	if (nr_new == 0)
 		return 0;