linux-kernel - Re: [PATCH v2 2/3] mmc: sdhci-omap: Add using external dma

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Date:   Mon, 3 Dec 2018 19:20:03 +0530
From:   Faiz Abbas <faiz_abbas@...com>
To:     Chunyan Zhang <zhang.chunyan@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>
CC:     <linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Mark Brown <broonie@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Sekhar Nori <nsekhar@...com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH v2 2/3] mmc: sdhci-omap: Add using external dma

Chunyan,

On 12/11/18 12:56 PM, Chunyan Zhang wrote:
> sdhci-omap can support both external dma controller via dmaengine framework
> as well as ADMA which standard SD host controller provides.
> 
> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
> ---
>  drivers/mmc/host/sdhci-omap.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-omap.c b/drivers/mmc/host/sdhci-omap.c
> index 88347ce..ccc79f2 100644
> --- a/drivers/mmc/host/sdhci-omap.c
> +++ b/drivers/mmc/host/sdhci-omap.c
> @@ -896,6 +896,7 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  	const struct of_device_id *match;
>  	struct sdhci_omap_data *data;
>  	const struct soc_device_attribute *soc;
> +	struct resource *regs;
>  
>  	match = of_match_device(omap_sdhci_match, dev);
>  	if (!match)
> @@ -908,6 +909,10 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  	}
>  	offset = data->offset;
>  
> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!regs)
> +		return -ENXIO;
> +
>  	host = sdhci_pltfm_init(pdev, &sdhci_omap_pdata,
>  				sizeof(*omap_host));
>  	if (IS_ERR(host)) {
> @@ -924,6 +929,7 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  	omap_host->timing = MMC_TIMING_LEGACY;
>  	omap_host->flags = data->flags;
>  	host->ioaddr += offset;
> +	host->mapbase = regs->start;
>  
>  	mmc = host->mmc;
>  	sdhci_get_of_property(pdev);
> @@ -991,6 +997,7 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  	host->mmc_host_ops.execute_tuning = sdhci_omap_execute_tuning;
>  	host->mmc_host_ops.enable_sdio_irq = sdhci_omap_enable_sdio_irq;
>  
> +	sdhci_switch_external_dma(host, true);

You should give the user a choice based on a dt property whether to use
ADMA or use external DMA. We might still want to use external DMA for
some platforms and ADMA for other platforms.

Thanks,
Faiz