[PATCH 2/3] mmc: omap_hsmmc: set max_segs based on dma engine limits
From: Joel Fernandes <hidden>
Date: 2013-07-18 16:47:42
Also in:
linux-devicetree, linux-mmc, linux-omap, linux-spi, lkml
Subsystem:
multimedia card (mmc), secure digital (sd) and sdio subsystem, omap hs mmc support, the rest · Maintainers:
Ulf Hansson, Linus Torvalds
From: Matt Porter <redacted> 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_slave_sg_limits() API. If the max_nr_segs limit is present, the value is used to configure mmc->max_segs appropriately. [Joel Fernandes [off-list ref]: Allocate sg_limits structure in client driver, and have the dmaengine implementation fill it up] Signed-off-by: Matt Porter <redacted> Acked-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Joel Fernandes <redacted> Cc: Mark Jackson <redacted> --- drivers/mmc/host/omap_hsmmc.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index eccedc7..b723095 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c@@ -1776,6 +1776,7 @@ 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 dma_slave_sg_limits dma_sg_limits; struct pinctrl *pinctrl; match = of_match_device(of_match_ptr(omap_mmc_of_match), &pdev->dev);
@@ -1952,6 +1953,14 @@ static int omap_hsmmc_probe(struct platform_device *pdev) goto err_irq; } + /* Some DMA Engines only handle a limited number of SG segments */ + ret = dma_get_slave_sg_limits(host->rx_chan, + DMA_SLAVE_BUSWIDTH_4_BYTES, + mmc->max_blk_size / 4, + &dma_sg_limits); + if (!ret && dma_sg_limits.max_seg_nr) + mmc->max_segs = dma_sg_limits.max_seg_nr; + /* Request IRQ for MMC operations */ ret = request_irq(host->irq, omap_hsmmc_irq, 0, mmc_hostname(mmc), host);
--
1.7.9.5