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

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

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?

>
> 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.