linux-kernel - Re: [RFC PATCH 1/3] of/device: manage resources similar to platform_device

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Message-ID: <CAL_JsqLW9PRktHntLquohH3x_bPgJrrn2Y2_8RYA_HnKhpTDHg@mail.gmail.com>
Date:	Tue, 13 Jan 2015 16:00:08 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Suman Anna <s-anna@...com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Pawel Moll <pawel.moll@....com>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	Felipe Balbi <balbi@...com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-omap <linux-omap@...r.kernel.org>
Subject: Re: [RFC PATCH 1/3] of/device: manage resources similar to platform_device_add

On Tue, Jan 13, 2015 at 3:25 PM, Suman Anna <s-anna@...com> wrote:
> Hi Rob,
>
> On 01/13/2015 02:38 PM, Rob Herring wrote:
>> On Wed, Jan 7, 2015 at 11:30 AM, Suman Anna <s-anna@...com> wrote:
>>> Drivers can use of_platform_populate() to create platform devices
>>> for children of the device main node, and a complementary API
>>> of_platform_depopulate() is provided to delete these child platform
>>> devices. The of_platform_depopulate() leverages the platform API
>>> for performing the cleanup of these devices.
>>>
>>> The platform device resources are managed differently between
>>> of_device_add and platform_device_add, and this asymmetry causes
>>> a kernel oops in platform_device_del during removal of the resources.
>>> Manage the platform device resources similar to platform_device_add
>>> to fix this kernel oops.
>>
>> This is a known issue and has been attempted to be fixed before (I
>> believe there is a revert in mainline). The problem is there are known
>> devicetrees which have overlapping resources and they will break with
>> your change.
>
> Are you referring to 02bbde7849e6 (Revert "of: use
> platform_device_add")?

I believe that's the one.

> That one seems to be in registration path, and
> this crash is in the unregistration path. If so, to fix the crash,
> should we be skipping the release_resource() for now in
> platform_device_del for DT nodes, or replace platform_device_unregister
> with of_device_unregister in of_platform_device_destroy()?

IIRC, the problem is inserting a resource twice on add from 2
different nodes, not the removal path. Perhaps we could make a
collision non-fatal for in the DT case. Grant may have some ideas on
what's needed here.

> This is a common crash and we cannot use of_platform_depopulate() today
> in drivers to complement of_platform_populate().

Yes, I know.

> Also, the platform_data crash is independent of this, I could reproduce
> that one even with using of_device_unregister in a loop in driver remove.

Missed this one. I'll reply to that patch.

Rob

>
> regards
> Suman
>
>>
>> Rob
>>
>>>
>>> Signed-off-by: Suman Anna <s-anna@...com>
>>> ---
>>>  drivers/of/device.c | 38 +++++++++++++++++++++++++++++++++++++-
>>>  1 file changed, 37 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>>> index 46d6c75c1404..fa27c1c71f29 100644
>>> --- a/drivers/of/device.c
>>> +++ b/drivers/of/device.c
>>> @@ -50,6 +50,8 @@ EXPORT_SYMBOL(of_dev_put);
>>>
>>>  int of_device_add(struct platform_device *ofdev)
>>>  {
>>> +       int i, ret;
>>> +
>>>         BUG_ON(ofdev->dev.of_node == NULL);
>>>
>>>         /* name and id have to be set so that the platform bus doesn't get
>>> @@ -63,7 +65,41 @@ int of_device_add(struct platform_device *ofdev)
>>>         if (!ofdev->dev.parent)
>>>                 set_dev_node(&ofdev->dev, of_node_to_nid(ofdev->dev.of_node));
>>>
>>> -       return device_add(&ofdev->dev);
>>> +       for (i = 0; i < ofdev->num_resources; i++) {
>>> +               struct resource *p, *r = &ofdev->resource[i];
>>> +
>>> +               if (!r->name)
>>> +                       r->name = dev_name(&ofdev->dev);
>>> +
>>> +               p = r->parent;
>>> +               if (!p) {
>>> +                       if (resource_type(r) == IORESOURCE_MEM)
>>> +                               p = &iomem_resource;
>>> +                       else if (resource_type(r) == IORESOURCE_IO)
>>> +                               p = &ioport_resource;
>>> +               }
>>> +
>>> +               if (p && insert_resource(p, r)) {
>>> +                       dev_err(&ofdev->dev, "failed to claim resource %d\n",
>>> +                               i);
>>> +                       ret = -EBUSY;
>>> +                       goto failed;
>>> +               }
>>> +       }
>>> +
>>> +       ret = device_add(&ofdev->dev);
>>> +       if (ret == 0)
>>> +               return ret;
>>> +
>>> +failed:
>>> +       while (--i >= 0) {
>>> +               struct resource *r = &ofdev->resource[i];
>>> +               unsigned long type = resource_type(r);
>>> +
>>> +               if (type == IORESOURCE_MEM || type == IORESOURCE_IO)
>>> +                       release_resource(r);
>>> +       }
>>> +       return ret;
>>>  }
>>>
>>>  int of_device_register(struct platform_device *pdev)
>>> --
>>> 2.2.1
>>>
>
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