If we want to get rid of the block layer bounce buffering for highmem we
need to ensure no segment spans multiple pages so that we can kmap it.
Add a flag to struct mmc_host so that we can handle the block and DMA
layer interactions in common code.
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
drivers/mmc/core/queue.c | 13 +++++++++++++
include/linux/mmc/host.h | 1 +
2 files changed, 14 insertions(+)
diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 35cc138b096d..71cd2411329e 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -370,6 +370,19 @@ static void mmc_setup_queue(struct mmc_queue *mq, struct
mmc_card *card)
blk_queue_max_segments(mq->queue, host->max_segs);
blk_queue_max_segment_size(mq->queue, host->max_seg_size);
+ /*
+ * If the host requires kmapping for PIO we need to ensure
+ * that no segment spans a page boundary.
+ */
+ if (host->need_kmap) {
+ unsigned int dma_boundary = host->max_seg_size - 1;
+
+ if (dma_boundary >= PAGE_SIZE)
+ dma_boundary = PAGE_SIZE - 1;
+ blk_queue_segment_boundary(mq->queue, dma_boundary);
+ dma_set_seg_boundary(mmc_dev(host), dma_boundary);
+ }
+
INIT_WORK(&mq->recovery_work, mmc_mq_recovery_handler);
INIT_WORK(&mq->complete_work, mmc_blk_mq_complete_work);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 4eadf01b4a93..87f8a89d2f70 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -397,6 +397,7 @@ struct mmc_host {
unsigned int doing_retune:1; /* re-tuning in progress */
unsigned int retune_now:1; /* do re-tuning at next req */
unsigned int retune_paused:1; /* re-tuning is temporarily
disabled */
+ unsigned int need_kmap:1; /* only allow single page
segments */
int rescan_disable; /* disable card detection */
int rescan_entered; /* used with nonremovable
devices */
--
2.20.1
