[PATCH 03/14] mmc: add a need_kmap flag to struct mmc_host

[Christoph Hellwig]

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 <hch@xxxxxx>
---
 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