From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH v4 09/14] mmc: omap_hsmmc: set max_segs based on dma
 engine limitations
Date: Fri, 11 Jan 2013 09:53:30 -0800
Message-ID: <20130111175330.GH14149@atomide.com>
References: <1357883330-5364-1-git-send-email-mporter@ti.com>
 <1357883330-5364-10-git-send-email-mporter@ti.com>
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To: Matt Porter <mporter@ti.com>
Cc: Sekhar Nori <nsekhar@ti.com>, Grant Likely <grant.likely@secretlab.ca>, Mark Brown <broonie@opensource.wolfsonmicro.com>, Benoit Cousson <b-cousson@ti.com>, Russell King <linux@arm.linux.org.uk>, Vinod Koul <vinod.koul@intel.com>, Rob Landley <rob@landley.net>, Chris Ball <cjb@laptop.org>, Devicetree Discuss <devicetree-discuss@lists.ozlabs.org>, Linux OMAP List <linux-omap@vger.kernel.org>, Linux ARM Kernel List <linux-arm-kernel@lists.infradead.org>, Linux DaVinci Kernel List <davinci-linux-open-source@linux.davincidsp.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Linux Documentation List <linux-doc@vger.kernel.org>, Linux MMC List <linux-mmc@vger.kernel.org>, Linux SPI Devel List <spi-devel-general@lists.sourceforge.net>, Arnd Bergmann <arnd@arndb.de>, Dan Williams <djbw@fb.com>, Rob Herring <rob.herring@calxeda.com>
List-Id: linux-omap@vger.kernel.org

* Matt Porter <mporter@ti.com> [130110 21:47]:
> 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.

Acked-by: Tony Lindgren <tony@atomide.com>
 
> Signed-off-by: Matt Porter <mporter@ti.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
>