From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Porter Subject: [PATCH 1/2] mmc: omap_hsmmc: set max_segs based on dma engine limits Date: Wed, 6 Mar 2013 23:16:38 -0500 Message-ID: <1362629799-22485-2-git-send-email-mporter@ti.com> References: <1362629799-22485-1-git-send-email-mporter@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1362629799-22485-1-git-send-email-mporter-l0cyMroinI0@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: Balaji T K , Chris Ball , Benoit Cousson , Tony Lindgren , Russell King Cc: Devicetree Discuss , Linux OMAP List , Linux MMC List , Linux Kernel Mailing List , Linux ARM Kernel List List-Id: devicetree@vger.kernel.org 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. Signed-off-by: Matt Porter Acked-by: Tony Lindgren --- drivers/mmc/host/omap_hsmmc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c index e79b12d..f74d2ef 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 dma_slave_sg_limits *dma_sg_limits; struct pinctrl *pinctrl; match = of_match_device(of_match_ptr(omap_mmc_of_match), &pdev->dev); @@ -1935,6 +1936,13 @@ static int omap_hsmmc_probe(struct platform_device *pdev) goto err_irq; } + /* Some DMA Engines only handle a limited number of SG segments */ + dma_sg_limits = dma_get_slave_sg_limits(host->rx_chan, + DMA_SLAVE_BUSWIDTH_4_BYTES, + mmc->max_blk_size / 4); + if (dma_sg_limits && 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