Re: [PATCH 3/3] PCI: rcar: fix bridge logic configuration accesses

[Valentine <valentine.barshak@cogentembedded.com>]

On 01/29/2014 10:42 AM, Simon Horman wrote:
> On Tue, Jan 28, 2014 at 11:41:29PM +0400, Valentine wrote:
>> On 01/28/2014 02:06 PM, Ben Dooks wrote:
>>> The bridge logic at slot 0 only supports reads up to 0x40 and the
>>> rest of the PCI configuration space for this slot is marked as
>>> reserved in the manual.
>>>
>>> Trying a read from offset 0x100 is producing an error from the
>>> bridge. With error interrupts enabled, the following is printed:
>>
>> I don't think this is a critical error.
>> The bridge works fine after an attempt to access the unsupported PCIe/PCI-X 2 area.
>>
>> If you want to prevent the access, I'm OK with it.
>> But I think it's better to do "if (where <= 0x100)"
>> and drop the slot check since all other slots do not support
>> access beyond 0x100 as well.
>>
>> The PCI code attempts to access beyond 0x100 only once when probing PCI bridges
>> to see if they support PCIe/PCI-X 2 area which is 4K.
>> The area beyond 0x40 is never accessed because the bridge does not expose any PCI capabilities.
>>
>>>
>>> pci-rcar-gen2 ee0d0000.pci: error irq: status 00000014
>>
>> Did you experience any problems other than this message
>> printed by the IRQ handler introduced by the previous patch?
>
> I am wondering if the documentation for the r8a7790 and r8a7791 are
> the same with regards to the <= 0x100 limit.
>

It is the same since it is neither a PCIe nor a PCI-X 2 device.

Thanks,
Val.

>>
>>>
>>> Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
>>> ---
>>> Cc: Valentine Barshak <valentine.barshak@cogentembedded.com>
>>> Cc: Simon Horman <horms@verge.net.au>
>>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>>> Cc: linux-pci@vger.kernel.org
>>> Cc: linux-sh@vger.kernel.org
>>> ---
>>>   drivers/pci/host/pci-rcar-gen2.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/pci/host/pci-rcar-gen2.c b/drivers/pci/host/pci-rcar-gen2.c
>>> index 01ba069..42f0105 100644
>>> --- a/drivers/pci/host/pci-rcar-gen2.c
>>> +++ b/drivers/pci/host/pci-rcar-gen2.c
>>> @@ -119,6 +119,10 @@ static void __iomem *rcar_pci_cfg_base(struct pci_bus *bus, unsigned int devfn,
>>>   	if (slot > 2)
>>>   		return NULL;
>>>
>>> +	/* bridge logic only has registers to 0x40 */
>>> +	if (slot == 0x0 && where >= 0x40)
>>> +		return NULL;
>>> +
>>>   	val = slot ? RCAR_AHBPCI_WIN1_DEVICE | RCAR_AHBPCI_WIN_CTR_CFG :
>>>   		     RCAR_AHBPCI_WIN1_HOST | RCAR_AHBPCI_WIN_CTR_CFG;
>>>
>>>
>>
>> Thanks,
>> Val.
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