linux-kernel - Re: [PATCH 4/4] dma-mapping: clear dev->dma_ops in arch_teardown_dma

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Date:   Wed, 26 Sep 2018 14:20:19 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christoph Hellwig <hch@....de>, Guenter Roeck <linux@...ck-us.net>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 4/4] dma-mapping: clear dev->dma_ops in arch_teardown_dma_ops

Christoph Hellwig <hch@....de> writes:

> Looking at the code I think this commit is simply broken for
> architectures not using arch_setup_dma_ops, but instead setting up
> the dma ops through arch specific magic.

I arch_setup_dma_ops() called from of_dma_configure(), but
pci_dma_configure() doesn't call that for this device:

static int pci_dma_configure(struct device *dev)
{
	...
	if (IS_ENABLED(CONFIG_OF) && bridge->parent &&
	    bridge->parent->of_node) {
		ret = of_dma_configure(dev, bridge->parent->of_node, true);

bridge->parent is NULL.

So I don't think arch_setup_dma_ops() would help here?

> I'll revert the patch.

Thanks.

cheers