[RFC PATCH v3 11/16] mmc: omap_hsmmc: limit max_segs with the EDMA DMAC

[Matt Porter <mporter-l0cyMroinI0@public.gmane.org>]

The EDMA DMAC has a hardware limitation that prevents supporting
scatter gather lists with any number of segments. Since the EDMA
DMA Engine driver sets the maximum segments to 16, we do the
same.

TODO: this will be replaced once the DMA Engine API supports an
API to query the DMAC's segment size limit.

Signed-off-by: Matt Porter <mporter-l0cyMroinI0@public.gmane.org>
---
 drivers/mmc/host/omap_hsmmc.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index b327cd0..52bab01 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1828,6 +1828,16 @@ static int __devinit omap_hsmmc_probe(struct platform_device *pdev)
 	 * as we want. */
 	mmc->max_segs = 1024;
 
+	/* Eventually we should get our max_segs limitation for EDMA by
+	 * querying the dmaengine API */
+	if (pdev->dev.of_node) {
+		struct device_node *parent = pdev->dev.of_node->parent;
+		struct device_node *node;
+		node = of_find_node_by_name(parent, "edma");
+		if (node)
+			mmc->max_segs = 16;
+	}
+
 	mmc->max_blk_size = 512;       /* Block Length at max can be 1024 */
 	mmc->max_blk_count = 0xFFFF;    /* No. of Blocks is 16 bits */
 	mmc->max_req_size = mmc->max_blk_size * mmc->max_blk_count;
-- 
1.7.9.5


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