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

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Date:   Tue, 13 Mar 2018 08:27:28 +0100
From:   "hch@....de" <hch@....de>
To:     Nipun Gupta <nipun.gupta@....com>
Cc:     Sinan Kaya <okaya@...eaurora.org>, "hch@....de" <hch@....de>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "johan@...nel.org" <johan@...nel.org>,
        "msuchanek@...e.de" <msuchanek@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Bharat Bhushan <bharat.bhushan@....com>,
        Leo Li <leoyang.li@....com>
Subject: Re: [PATCH] dma-mapping: move dma configuration to bus
        infrastructure

On Tue, Mar 13, 2018 at 04:22:53AM +0000, Nipun Gupta wrote:
> > Isn't this one or the other one but not both?
> > 
> > Something like:
> > 
> > if (dev->of_node)
> > 	of_dma_deconfigure(dev);
> > else
> > 	acpi_dma_deconfigure(dev);
> > 
> > should work.
> 
> I understand your point. Seems reasonable as we should not expect
> the 'of/acpi DMA deconfigure' API to not fail when they are not configured.
> 
> But, here we would also need to get dma_device (just as we get in
> 'pci_dma_configure') and need a check on it as for PCI there 'of_node'
> is present in the dma_dev.

Both of_dma_deconfigure and acpi_dma_deconfigure just end up calling
arch_teardown_dma_ops.  So my preference would be to just remove
of_dma_deconfigure and acpi_dma_deconfigure and call arch_teardown_dma_ops
as a prep patch before this one.