linux-kernel - Re: [PATCH V5 8/9] PCI: OF: Move of_pci_dma_configure() to pci_dma

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Date:	Wed, 18 Nov 2015 12:00:32 +0000
From:	Robin Murphy <robin.murphy@....com>
To:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	bhelgaas@...gle.com, rjw@...ysocki.net, lenb@...nel.org,
	catalin.marinas@....com, will.deacon@....com,
	"arnd@...db.de" <arnd@...db.de>
Cc:	thomas.lendacky@....com, herbert@...dor.apana.org.au,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, hanjun.guo@...aro.org,
	davem@...emloft.net, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V5 8/9] PCI: OF: Move of_pci_dma_configure() to
 pci_dma_configure()

+Arnd

On 17/11/15 15:00, Robin Murphy wrote:
> Hi Suravee,
>
> On 28/10/15 22:50, Suravee Suthikulpanit wrote:
>> This patch move of_pci_dma_configure() to a more generic
>> pci_dma_configure(), which can be extended by non-OF code (e.g. ACPI).
>>
>> This has no functional change.
>
> Unfortunately, it appears that it does...
>
>> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>> Acked-by: Rob Herring <robh+dt@...nel.org>
>> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
>> Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>
>> CC: Rafael J. Wysocki <rjw@...ysocki.net>
[...]
>> +/**
>> + * pci_dma_configure - Setup DMA configuration
>> + * @dev: ptr to pci_dev struct of the PCI device
>> + *
>> + * Function to update PCI devices's DMA configuration using the same
>> + * info from the OF node of host bridge's parent (if any).
>> + */
>> +static void pci_dma_configure(struct pci_dev *dev)
>> +{
>> +    struct device *bridge = pci_get_host_bridge_device(dev);
>> +
>> +    if (IS_ENABLED(CONFIG_OF) && dev->dev.of_node) {
>
> Previously I was seeing of_dma_configure, and thus of_iommu_configure,
> called for every PCI device on Juno. The check above now prevents this
> happening, since the PCI devices are probed directly from the bus and
> don't have OF nodes of their own. They now get left in some
> half-configured state where arch_setup_dma_ops isn't called either.

Just to follow up on that, Arnd's patch to tidy up dma_get_ops (now 
queued[1]) makes this even worse, since preventing arch_setup_dma_ops 
being called means the PCI devices now get the dummy DMA ops which leave 
the drivers failing to probe at all, IOMMU hacks or not :(

Robin.

[1]:https://git.kernel.org/cgit/linux/kernel/git/arm64/linux.git/commit/?h=fixes/core&id=1dccb598df549d892b6450c261da54cdd7af44b4

> Should this be checking bridge->parent->of_node rather than
> dev->dev.of_node (which seems to work), or am I missing something?
>
> Sorry I don't really have the bandwidth to look into this in detail
> myself, right now I'm just trying to get my magic hacks rebased ;)
>
> Robin.
>
>> +        if (bridge->parent)
>> +            of_dma_configure(&dev->dev, bridge->parent->of_node);
>> +    }
>> +
>> +    pci_put_host_bridge_device(bridge);
>> +}

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