[PATCH] mmc: core: don't decrement qty when calculating max_discard

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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-tegra" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [ARM Kernel]     [Linux ARM]     [Linux ARM MSM]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux