linux-kernel - Re: [PATCH] dma-mapping: move dma configuration to bus infrastructure

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Date:   Tue, 13 Mar 2018 08:34:48 +0100
From:   Christoph Hellwig <hch@....de>
To:     Nipun Gupta <nipun.gupta@....com>
Cc:     hch@....de, robin.murphy@....com, linux@...linux.org.uk,
        gregkh@...uxfoundation.org, m.szyprowski@...sung.com,
        bhelgaas@...gle.com, dmitry.torokhov@...il.com,
        rafael.j.wysocki@...el.com, jarkko.sakkinen@...ux.intel.com,
        linus.walleij@...aro.org, johan@...nel.org, msuchanek@...e.de,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH] dma-mapping: move dma configuration to bus
        infrastructure

> +int amba_dma_configure(struct device *dev)
> +{
> +	enum dev_dma_attr attr;
> +	int ret = 0;
> +
> +	if (dev->of_node) {
> +		ret = of_dma_configure(dev, dev->of_node);
> +	} else if (has_acpi_companion(dev)) {
> +		attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
> +		if (attr != DEV_DMA_NOT_SUPPORTED)
> +			ret = acpi_dma_configure(dev, attr);
> +	}
> +
> +	return ret;

This code sniplet is duplicated so many times that I think we should
just have some sort of dma_common_configure() for it that the various
busses can use.

> +void amba_dma_deconfigure(struct device *dev)
> +{
> +	of_dma_deconfigure(dev);
> +	acpi_dma_deconfigure(dev);
> +}

As mention in my previous reply I think we don't even need a deconfigure
callback at this point - just remove the ACPI and OF wrappers and
clear the dma ops.

Also in this series we should replace the force_dma flag by use of the
proper method, e.g. give a force parameter to of_dma_configure and the
new dma_common_configure helper that the busses that want it can set.