linux-kernel - Re: [PATCH] pci: of : fix BUG: unable to handle kernel

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Message-ID: <55005E82.4050607@ti.com>
Date:	Wed, 11 Mar 2015 11:25:54 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	Rob Herring <robherring2@...il.com>
CC:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Arnd Bergmann <arnd@...db.de>,
	Suravee Suthikulanit <Suravee.Suthikulpanit@....com>,
	Will Deacon <will.deacon@....com>,
	Joerg Roedel <joro@...tes.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [PATCH] pci: of : fix BUG: unable to handle kernel

On 03/11/2015 08:35 AM, Rob Herring wrote:
> On Tue, Mar 10, 2015 at 10:25 AM, Murali Karicheri<m-karicheri2@...com>  wrote:
>> On some platforms such as that based on x86, ia64 etc, root bus is
>> created with parent node passed in as NULL to pci_create_root_bus().
>> On these platforms, the patch series "PCI: get DMA configuration from
>> parent device" when applied causes kernel crash. So add a check for this
>> in of_pci_dma_configure()
>
> Wouldn't these arches have OF disabled and call an empty function?
The current patch series does have a empty function if OF is disabled.
> Regardless, we still need this.
These archs have OF enabled, but they call  pci_create_root_bus() with 
NULL parent node passed in. That is why the crash happens.

Murali
>
>> Signed-off-by: Murali Karicheri<m-karicheri2@...com>
>
> I'm assuming Bjorn will apply this.
>
> Acked-by: Rob Herring<robh@...nel.org>
>
>> ---
>>   drivers/of/of_pci.c |    4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
>> index 86d3c38..a8e485c 100644
>> --- a/drivers/of/of_pci.c
>> +++ b/drivers/of/of_pci.c
>> @@ -129,6 +129,10 @@ 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);
>>
>> +       /* Some platforms can have bridge->parent set to NULL */
>> +       if (!bridge->parent)
>> +               return;
>> +
>>          of_dma_configure(dev, bridge->parent->of_node);
>>          pci_put_host_bridge_device(bridge);
>>   }
>> --
>> 1.7.9.5
>>
> --
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-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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