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SubjectRe: [PATCH v2 2/3] mmc: sdhci-omap: Add using external dma
Hi Faiz,

Thanks for the review and test!

On Mon, 3 Dec 2018 at 21:47, Faiz Abbas <faiz_abbas@ti.com> wrote:
>
> 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@linaro.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.

With the current patchset, if users want to use external DMA, they
need to add 'dmas' in device tree, like patch 3 shows:
+ dmas = <&sdma 61 &sdma 62>;
+ dma-names = "tx", "rx";
Otherwise, sdhci.c will switch back to use the DMA/PIO integrated in
standard SDHCI.

But I think your suggestion makes sense, will add the below graph in
next version:

+ /* Switch to external DMA only if there is the "dmas" property */
+ if (of_find_property(dev->of_node, "dmas", NULL))
+ sdhci_switch_external_dma(host, true);

Thanks,
Chunyan

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