Re: [PATCH v4 4/6] of/pci: add of_pci_dma_configure() update dma configuration

[Murali Karicheri]

On 01/26/2015 06:59 PM, Bjorn Helgaas wrote:
> On Mon, Jan 26, 2015 at 5:25 PM, Murali Karicheri<m-karicheri2@xxxxxx>  wrote:
> > On 01/23/2015 06:41 PM, Bjorn Helgaas wrote:
> > > On Fri, Jan 23, 2015 at 05:32:37PM -0500, Murali Karicheri 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.
  -- Cut ---
> > > > Signed-off-by: Murali Karicheri<m-karicheri2@xxxxxx>
> > > > ---
> > > >    drivers/of/of_pci.c    |   39 +++++++++++++++++++++++++++++++++++++++
> > > >    include/linux/of_pci.h |   12 ++++++++++++
> > > >    2 files changed, 51 insertions(+)
> > > >
> > > > diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> > > > index 88471d3..34878c9 100644
> > > > --- a/drivers/of/of_pci.c
> > > > +++ b/drivers/of/of_pci.c
> > > > @@ -2,6 +2,7 @@
> > > >    #include<linux/export.h>
> > > >    #include<linux/of.h>
> > > >    #include<linux/of_address.h>
> > > > +#include<linux/of_device.h>
> > > >    #include<linux/of_pci.h>
> > > >    #include<linux/slab.h>
> > > >
> > > > @@ -229,6 +230,44 @@ parse_failed:
> > > >          return err;
> > > >    }
> > > >    EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
> > > > +
> > > > +/**
> > > > + * of_get_pci_root_bridge_parent - get the OF node of the root bridge's
> > > > parent
> > > > + * @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 root bridge device's parent
> > > > device.
> > > > + */
> > > > +struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev)
> > >
> > >
> > > I'm not an OF person, but this interface seems like it might be too
> > > special-purpose.  Maybe it would be enough to add
> > > "of_get_pci_root_bridge()", and the caller could do this:
> > >
> > >       struct device *bridge = of_get_pci_root_bridge(dev);
> > >       struct device_node *parent_np = bridge->parent->of_node;
> > >
> > > Also, the name "of_get_..." suggests that it increments a refcount, as
> > > of_get_parent() does.  But you aren't doing anything with the refcount.
> > >
> > > But I guess an "of_get_pci_root_bridge()" isn't doing anything OF-related,
> > > so maybe we should just add a "pci_get_host_bridge(struct pci_dev *)"
> > > to PCI instead.
> >
> >
> > Bjorn,
> >
> > Thanks for the comment.
> >
> > I think adding pci_get_host_bridge() is a good idea. There is already
> > similar function in host-bridge.c. I have added this function re-using
> > existing function find_pci_root_bus(). See the incremental diff below after
> > this change. Does this look good?
>
> I like the implementation, but I think either we need to take a
> reference on the host bridge, or change the name to  something like
> "pci_find_host_bridge()", because using "_get_" is conventional for
> functions that acquire a reference.
>
> Since host bridges are hot-pluggable, at least in theory, I vote for
> taking a reference.  Then of course, you'd have to add code to drop
> the reference when you're finished with it.
Bjorn,

Thanks. I agree with your suggestion even though the convention is not 
followed fully :) of_pci_get_devfn(), of_get_pci_domain_nr(), 
of_pci_get_host_bridge_resources() are some of those functions not 
following the convention. I plan to change the function as below. Also 
want to name functions as pci_get/put_host_bridge_device() as existing 
function find_pci_host_bridge() is actually returning ptr to struct 
pci_host_bridge  vs the new function returning ptr to device. Here are 
the new functions and how they will be used. Please review and respond 
so that I can avoid a re-spin.

in linux/include/pci.h add the prototypes of 
pci_get/put_host_bridge_device().

in drivers/pci/host-bridge.c add two new functions.

struct device *pci_get_host_bridge_device(struct pci_dev *dev)
{
	struct pci_bus *root_bus = find_pci_root_bus(dev->bus);
	struct device *bridge = root_bus->bridge;

	kobject_get(&bridge->kobj);
	return bridge;
}

void  pci_put_host_bridge_device(struct pci_dev *dev)
{
	struct pci_bus *root_bus = find_pci_root_bus(dev->bus);
	struct device *bridge = root_bus->bridge;

	kobject_put(&bridge->kobj);
}

drivers/of/of_pci.c

void of_pci_dma_configure(struct pci_dev *pci_dev)
{
	struct device *dev = &pci_dev->dev;
	struct device *bridge = pci_get_host_bridge_device(pci_dev);

	of_dma_configure(dev, bridge->parent->of_node);
	pci_put_host_bridge_device(pci_dev);
}

Murali

> Bjorn

> > > >
> >
> >
> > --
> > Murali Karicheri
> > Linux Kernel, Texas Instruments


--
Murali Karicheri
Linux Kernel, Texas Instruments
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