[PATCH v4 3/3] mmc: core: Optimize the mmc erase size alignment

[Baolin Wang]

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.w...@linaro.org>
Tested-by: Shawn Lin <shawn....@rock-chips.com>
---
 drivers/mmc/core/core.c |   34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 5f93eef..e014949 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2209,19 +2209,37 @@ static unsigned int mmc_align_erase_size(struct 
mmc_card *card,
 {
        unsigned int from_new = *from, nr_new = nr, rem;
 
-       rem = from_new % card->erase_size;
-       if (rem) {
-               rem = card->erase_size - rem;
-               from_new += 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;
-       }
 
-       rem = nr_new % card->erase_size;
-       if (rem)
-               nr_new -= rem;
+               nr_new = round_down(nr_new, card->erase_size);
+       } else {
+               rem = from_new % card->erase_size;
+               if (rem) {
+                       rem = card->erase_size - rem;
+                       from_new += rem;
+                       if (nr_new > rem)
+                               nr_new -= rem;
+                       else
+                               return 0;
+               }
+
+               rem = nr_new % card->erase_size;
+               if (rem)
+                       nr_new -= rem;
+       }
 
        if (nr_new == 0)
                return 0;
-- 
1.7.9.5