On Fri, 2014-07-25 at 16:31 +0300, Andy Shevchenko wrote:
> Some chipsets use the function 0 for DMA on other functions of a
> multifunctional device. One of the example is Intel EG20T PCH. This is also
> applicable to Lynxpoint PCH when LPSS devices are switched to PCI mode.
>
> This patch exports a useful helper to get a device of the DMA. This device is
> needed to request a DMA channel from a proper controller.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> drivers/pci/quirks.c | 2 +-
> include/linux/pci.h | 9 +++++++++
> 2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 80c2d01..8352e5b 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3517,7 +3517,7 @@ static struct pci_dev *pci_func_0_dma_source(struct pci_dev *dev)
> if (!PCI_FUNC(dev->devfn))
> return pci_dev_get(dev);
>
> - return pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
> + return pci_get_dma_device(dev);
> }
>
> static const struct pci_dev_dma_source {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 61978a4..86caab7 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1575,6 +1575,15 @@ static inline int pci_dev_specific_acs_enabled(struct pci_dev *dev,
> static inline void pci_dev_specific_enable_acs(struct pci_dev *dev) { }
> #endif
>
> +/*
> + * Some chipsets use the function 0 for DMA on other functions of a
> + * multifunctional device.
> + */
> +static inline struct pci_dev *pci_get_dma_device(struct pci_dev *dev)
> +{
> + return pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
> +}
> +
> void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
> void pcim_iounmap(struct pci_dev *pdev, void __iomem *addr);
> void __iomem * const *pcim_iomap_table(struct pci_dev *pdev);
You've created a very generic function for a very specific problem. I
can't just call this on any random device and expect it to work
correctly. What about all the other device which use function 1 for
their DMA alias. We've just added infrastructure in PCI to support DMA
aliases, see pci_for_each_dma_alias(). Please use this instead. Quirks
can be added to set the dma_alias_devfn and
PCI_DEV_FLAGS_DMA_ALIAS_DEVFN to indicate that it's valid. Thanks,
Alex
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