[PATCH v5 09/14] mmc: omap_hsmmc: set max_segs based on dma engine limitations

Matt Porter
2013-01-15T20:28:43Z

The EDMA DMAC has a hardware limitation that prevents supporting
scatter gather lists with any number of segments. The DMA Engine
API reports the maximum number of segments a channel can support
via the optional dma_get_channel_caps() API. If the nr_segs
capability is present, the value is used to configure mmc->max_segs
appropriately.

Signed-off-by: Matt Porter <mporter@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
---
drivers/mmc/host/omap_hsmmc.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index e79b12d..f74bd69 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -1769,6 +1769,7 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
const struct of_device_id *match;
dma_cap_mask_t mask;
unsigned tx_req, rx_req;
+ struct dmaengine_chan_caps *dma_chan_caps;
struct pinctrl *pinctrl;

match = of_match_device(of_match_ptr(omap_mmc_of_match), &pdev->dev);
@@ -1935,6 +1936,11 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
goto err_irq;
}

+ /* Some DMA Engines only handle a limited number of SG segments */
+ dma_chan_caps = dma_get_channel_caps(host->rx_chan, DMA_DEV_TO_MEM);
+ if (dma_chan_caps && dma_chan_caps->seg_nr)
+ mmc->max_segs = dma_chan_caps->seg_nr;
+
/* Request IRQ for MMC operations */
ret = request_irq(host->irq, omap_hsmmc_irq, 0,
mmc_hostname(mmc), host);
--
1.7.9.5