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Message-ID: <CAErSpo4Awgqu0ZtoMm0XSZzhnYtXh3xxH2OJMkyth5YDR9GUiA@mail.gmail.com>
Date: Tue, 27 Jan 2015 12:42:11 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Murali Karicheri <m-karicheri2@...com>
Cc: linux-arm <linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"open list:INTEL IOMMU (VT-d)" <iommu@...ts.linux-foundation.org>,
Joerg Roedel <joro@...tes.org>,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Will Deacon <will.deacon@....com>,
Russell King <linux@....linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Subject: Re: [PATCH v4 4/6] of/pci: add of_pci_dma_configure() update dma configuration
On Tue, Jan 27, 2015 at 12:14 PM, Murali Karicheri <m-karicheri2@...com> wrote:
> On 01/26/2015 06:59 PM, Bjorn Helgaas wrote:
>>
>> On Mon, Jan 26, 2015 at 5:25 PM, Murali Karicheri<m-karicheri2@...com>
>> 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@...com>
>>>>> ---
>>>>> 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
>
>> Bjorn
>>
>
>>>>>
>>>
>>>
>>> --
>>> Murali Karicheri
>>> Linux Kernel, Texas Instruments
>
>
>
> --
> Murali Karicheri
> Linux Kernel, Texas Instruments
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