linux-kernel - Re: [PATCH v2 1/2] of/pci: add of_pci_dma

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Date:	Fri, 26 Dec 2014 13:33:23 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Will Deacon <will.deacon@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] of/pci: add of_pci_dma_configure() update dma configuration

On Wed, Dec 24, 2014 at 4:11 PM, Murali Karicheri <m-karicheri2@...com> wrote:
> Add of_pci_dma_configure() to allow updating the dma configuration
> of the pci device using the configuration from DT of the parent of
> the root bridge device.
>
> Signed-off-by: Murali Karicheri <m-karicheri2@...com>
> ---
>  drivers/of/of_pci.c    |   73 ++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_pci.h |   12 ++++++++
>  2 files changed, 85 insertions(+)
>
> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> index 88471d3..6d43f59 100644
> --- a/drivers/of/of_pci.c
> +++ b/drivers/of/of_pci.c
> @@ -229,6 +229,79 @@ parse_failed:
>         return err;
>  }
>  EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
> +
> +/**
> + * of_get_pci_root_bridge_parent - Helper function to get the OF node of
> + *             the root bridge's parent

I believe this has to be a one line description for DocBook.

> + * @dev: ptr to pci_dev struct of the pci device
> + *
> + * This function will traverse the bus up to the root bus starting with
> + * the child and return the of node ptr to bridge device's parent device.
> + */
> +struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev)
> +{
> +       struct pci_bus *bus = dev->bus;
> +       struct device *bridge;
> +
> +       while (!pci_is_root_bus(bus))
> +               bus = bus->parent;
> +       bridge = bus->bridge;
> +
> +       return bridge->parent->of_node;
> +}
> +EXPORT_SYMBOL_GPL(of_get_pci_root_bridge_parent);
> +
> +/**
> + * of_pci_dma_configure - Setup DMA configuration
> + * @dev: ptr to pci_dev struct of the pci device
> + *
> + * Try to get PCI devices's DMA configuration from DT and update it
> + * accordingly. This is similar to of_dma_configure() in of/platform.c
> + */
> +void of_pci_dma_configure(struct pci_dev *pci_dev)
> +{
> +       struct device *dev = &pci_dev->dev;
> +       u64 dma_addr, paddr, size;
> +       struct device_node *parent_np;
> +       unsigned long offset;
> +       bool coherent;
> +       int ret;
> +
> +       parent_np = of_get_pci_root_bridge_parent(pci_dev);
> +
> +       if (parent_np) {

Save a level of indentation and do:

if (!parent_np)
  return;

> +               /*
> +                * Set default dma-mask to 32 bit. Drivers are expected to setup
> +                * the correct supported dma_mask.
> +                */
> +               dev->coherent_dma_mask = DMA_BIT_MASK(32);
> +
> +               /*
> +                * Set it to coherent_dma_mask by default if the architecture
> +                * code has not set it.
> +                */
> +               if (!dev->dma_mask)
> +                       dev->dma_mask = &dev->coherent_dma_mask;
> +
> +               ret = of_dma_get_range(parent_np, &dma_addr, &paddr, &size);
> +               if (ret < 0) {
> +                       dma_addr = offset = 0;
> +                       size = dev->coherent_dma_mask + 1;
> +               } else {
> +                       offset = PFN_DOWN(paddr - dma_addr);
> +                       dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
> +               }
> +               dev->dma_pfn_offset = offset;
> +
> +               coherent = of_dma_is_coherent(parent_np);
> +               dev_dbg(dev, "device is%sdma coherent\n",
> +                       coherent ? " " : " not ");
> +
> +               arch_setup_dma_ops(dev, dma_addr, size, NULL, coherent);

This is the same code as of_dma_configure. The only difference I see
is which node ptr is passed to of_dma_get_range. You need to make that
a function param of of_dma_configure.

of_dma_configure also has iommu handling now. You will probably need
something similar for PCI in that you setup an iommu based on the root
bus DT properties.

Rob
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