[RFC PATCH 08/13] mmc: omap_hsmmc: limit max_segs with the EDMA DMAC

[Matt Porter]

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.

Note: this can be removed once the DMA Engine API supports an
API to query the DMAC's segment limitations.

Signed-off-by: Matt Porter <mporter at ti.com>
---
 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 c82d0ab..61b54ee 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1885,6 +1885,16 @@ 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