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

[Murali Karicheri <m-karicheri2-l0cyMroinI0@public.gmane.org>]

On 01/27/2015 01:42 PM, Bjorn Helgaas wrote:
> On Tue, Jan 27, 2015 at 12:14 PM, Murali Karicheri<m-karicheri2-l0cyMroinI0@public.gmane.org>  wrote:
>> On 01/26/2015 06:59 PM, Bjorn Helgaas wrote:
>>>
>>> On Mon, Jan 26, 2015 at 5:25 PM, Murali Karicheri<m-karicheri2-l0cyMroinI0@public.gmane.org>
>>> 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-l0cyMroinI0@public.gmane.org>
>>>>>> ---
>>>>>>     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)"

Agree with both. Will become part of my v5 of the series. I am adding 
this as a separate commit.

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


-- 
Murali Karicheri
Linux Kernel, Texas Instruments