Re: [PATCH] PCIE: pcie_set_readrq must not be allowed by PCIE EP driver

[Pratyush Anand <pratyush.anand@st.com>]

Hi Tejun,

Its a long pending patch.
Any decision on this patch.

Regards
Pratyush

On 3/16/2011 12:35 PM, pratyush wrote:
> Hello Hemant,
>
> On 3/16/2011 9:43 AM, Pedanekar, Hemant wrote:
>>> What happens in your case? Does it not work, if you do not
>>>> modify sil driver?
>>>>
>> I also require to modify the sil driver to avoid setting max RRQ to 4096
>> otherwise the data transfer over PCIe does not work. The RC responds with
>> "Unsupported Request" for read request of size greater than 256 bytes.
>>
>> The other problem is, there is no way for peers to know that the other
>> device cannot handle RRQ of size beyond certain limit. At least I am not
>> aware of any bits in PCIe configuration space which advertise this. Do you
>> know of any such?
>>
>> While, there is "Max RRQ size" field in device control register which only
>> controls outbound RRQ size.
>>
>> This restriction probbaly will complicate more when the device with such
>> RRQ limitation is a EP, in such case, no one else than the EP (and its driver)
>> would know about this limitation and need to force others (including RC) to
>> reduce the max RRQ size.
>>
>
> Yes, I am agreed with you. I do not see any way to inform its peers about request
> limit. So I think that a EP driver should not be allowed to call any function which
> changes EP's RRQ size. It should always be RC driver which sets these values as
> per max capability of the link.
>
> Currently I am managing it with postinit hook of RC driver. But can be part of
> common pci stack.
>
> You can see my way of handling it at
> http://www.spinics.net/lists/linux-pci/msg09897.html
>
> Regards
> Pratyush