On Wed, Sep 30, 2015 at 2:30 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
> On Wed, Sep 30, 2015 at 4:17 PM, Duc Dang <dhdang@xxxxxxx> wrote:
>> On Tue, Sep 29, 2015 at 9:47 AM, Rob Herring <robh@xxxxxxxxxx> wrote:
>>> + several affected driver maintainers
>>>
>>> On Mon, Sep 28, 2015 at 6:05 PM, Russell King - ARM Linux
>>> <linux@xxxxxxxxxxxxxxxx> wrote:
>>>> On Mon, Sep 28, 2015 at 05:42:20PM -0500, Rob Herring wrote:
>>>>> On Mon, Sep 28, 2015 at 5:08 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>>>>> > Hi Rob,
>>>>> >
>>>>> > Russell pointed out a problem with 1f94a94f67e1 ("PCI: Add generic config
>>>>> > accessors"). pci_generic_config_write32() does a read/modify/write if the
>>>>> > size is less than 32 bits, so I think we have problem if this is used with
>>>>> > 8- or 16-bit registers that contain RW1C bits. Any thoughts on how we can
>>>>> > fix this?
>>>>>
>>>>> My series didn't change access sizes unless I made a made a mistake
>>>>> somewhere, so the problem should have existed before.
>>>>>
>>>>> Is it known addresses we need to deal with? We could do special case
>>>>> handling of certain addresses to mask out RW1C bits. This could be in
>>>>> the generic functions or in wrappers around the generic functions.
>>>>> There's already some similar examples of special address handling
>>>>> IIRC.
>>>>
>>>> I think this originally came into being because Intel decided that their
>>>> IOP platforms wouldn't support anything except 32-bit accesses, and
>>>> cargo cult programming took over. I complained about it on the Intel IOP
>>>> platforms, but obviously if the hardware doesn't support anything else
>>>> then your stuck with it.
>>>
>>> What about SA1100 nanoengine?
>>>
>>> Others are Tegra, XGene, iproc, and maybe rcar. These are all
>>> relatively active platforms, so hopefully some testing can be done.
>>
>> On X-Gene, so far I don't see anything strange after switching to use
>> pci_generic_config_write32 with all the cards that I can test.
>
> You mean switching to use pci_generic_config_write, right?
Hi Rob,
I meant even using pci_generic_config_write32 , all the cards that I
have right now are still running fine.
>
>>
>> But looks like it's still safer to use pci_generic_config_write
>> instead as this will make sure no unexpected read-modify-write will
>> happen?
>
> Yes. You can also change xgene_pcie_config_read32 to use
> pci_generic_config_read instead to simplify the function some.
>
> Rob
Regards,
Duc Dang.
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
