On Tue, Jan 27, 2015 at 12:14 PM, Murali Karicheri [off-list ref] wrote:

On 01/26/2015 06:59 PM, Bjorn Helgaas wrote:

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On Mon, Jan 26, 2015 at 5:25 PM, Murali Karicheri[off-list ref]
wrote:

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On 01/23/2015 06:41 PM, Bjorn Helgaas wrote:

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On Fri, Jan 23, 2015 at 05:32:37PM -0500, Murali Karicheri wrote:

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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 ---

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Signed-off-by: Murali Karicheri<redacted>
---
   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;
}

Looks good to me.

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);
}

I think I would pass in the "struct device *" here so we don't have to
call find_pci_root_bus() again.

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);

Then this would become "pci_put_host_bridge_device(bridge)"

}

Murali

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Bjorn

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--
Murali Karicheri
Linux Kernel, Texas Instruments

--
Murali Karicheri
Linux Kernel, Texas Instruments