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 13:41:39 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Robin Murphy <robin.murphy@....com>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	bhelgaas@...gle.com, rjw@...ysocki.net, lenb@...nel.org,
	catalin.marinas@....com, will.deacon@....com,
	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()

On Wednesday 18 November 2015 12:00:32 Robin Murphy wrote:
> On 17/11/15 15:00, Robin Murphy wrote:
> > On 28/10/15 22:50, Suravee Suthikulpanit wrote:
> >> 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 

Ok, glad we found that with my patch then. We really have to
configure the DMA (offset/size/coherency/iommu) for all devices that might
be masters, otherwise things can randomly go wrong.

	ARnd
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