Adjust unaligned write accesses spanning preferred align
size into two accesses - an unaligned and an aligned access.
This is meant to be used for card quirks, and is off
by default. A limiting value in transfer size
for this adjustment is available, as on some cards there is a
perf decrease for larger transfers.
Signed-off-by: Andrei Warkentin <andreiw@xxxxxxxxxxxx>
---
drivers/mmc/card/block.c | 43 +++++++++++++++++++++++++++++++++++++++++++
1 files changed, 43 insertions(+), 0 deletions(-)
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 913f394..a8f18c7 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -63,6 +63,8 @@ struct mmc_blk_data {
unsigned int usage;
unsigned int read_only;
+ unsigned int write_align_size;
+ unsigned int write_align_limit;
};
static DEFINE_MUTEX(open_lock);
@@ -312,6 +314,43 @@ out:
return err ? 0 : 1;
}
+/*
+ * If the request is not aligned, split it into an unaligned
+ * and an aligned portion. Here we can adjust
+ * the size of the MMC request and let the block layer request handle
+ * deal with generating another MMC request.
+ */
+
+static void mmc_adjust_write(struct mmc_card *card,
+ struct mmc_request *mrq)
+{
+ unsigned int left_in_page;
+ unsigned int wa_size_blocks;
+ struct mmc_blk_data *md = mmc_get_drvdata(card);
+
+ if (!md->write_align_size)
+ return;
+
+ if (md->write_align_limit &&
+ (md->write_align_limit / mrq->data->blksz)
+ < mrq->data->blocks)
+ return;
+
+ wa_size_blocks = md->write_align_size / mrq->data->blksz;
+ left_in_page = wa_size_blocks -
+ (mrq->cmd->arg % wa_size_blocks);
+
+ /* Aligned access. */
+ if (left_in_page == wa_size_blocks)
+ return;
+
+ /* Not straddling page boundary. */
+ if (mrq->data->blocks <= left_in_page)
+ return;
+
+ mrq->data->blocks = left_in_page;
+}
+
static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
{
struct mmc_blk_data *md = mq->data;
@@ -339,6 +378,10 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
brq.stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
brq.data.blocks = blk_rq_sectors(req);
+ /* Check for unaligned accesses straddling pages. */
+ if (rq_data_dir(req) == WRITE)
+ mmc_adjust_write(card, &brq.mrq);
+
/*
* The block layer doesn't support all sector count
* restrictions, so we need to be prepared for too big
--
1.7.0.4
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