Re: [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



>> OK. Sorry, I have one last question, because domain will be used to calculate the address used to
>> access PCI hardware config registers. So if DTS file doesn't report the domain, how do we know
>> we would access the right registers when we use the auto increment domain vaule ?
> 
> That's a good question and sides with Arnd's suggestion to try to mandate the presence of the PCI
> domain in the DTS. However, by grepping through the source code, it looks like the architectures
> that use the domain number for reading config registers (x86-based) are non-DT architectures,
> while DT-aware arches seem to ignore the domain number except when printing out messages. Is that
> another confirmation that most DT-aware architectures have only run with domain_nr = 0?
> 

Arnd's suggestion is make sense to me, thanks for Bjorn's detailed explanation, now I know domain_nr
is purely internal to kernel in DT-aware platform, it's not needed when access PCI config space.

Thanks!
Yijing.

> 
>> Has there a mechanism to make sure system can access the correct registers by the domain ?
> 
> Not as such if you look with x86 glasses. With the exception of powerpc all other architecures
> seem to happily assume domain_nr = 0 and ignore it in the computation of configuration registers
> offsets.
> 
> Best regards,
> Liviu
> 
>>
>> Thanks!
>> Yijing.
>>
>>>
>>> Best regards,
>>> Liviu
>>>
>>>>
>>>> PCI get domain by ACPI "_SEG" in IA64(drivers/acpi/pci_root.c)
>>>> ......
>>>> 	status = acpi_evaluate_integer(handle, METHOD_NAME__SEG, NULL,
>>>> 				       &segment);
>>>> 	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
>>>> 		dev_err(&device->dev,  "can't evaluate _SEG\n");
>>>> 		result = -ENODEV;
>>>> 		goto end;
>>>> 	}
>>>> .......
>>>>
>>>> Thanks!
>>>> Yijing.
>>>>
>>>>>
>>>>>> This function
>>>>>> is just a weird mixture of data retrieval and allocation. I think you
>>>>>> need to separate it into 2 functions.
>>>>>
>>>>> It is meant to do allocation with the retrieval being a short-cut (or fine
>>>>> control if you want).
>>>>>
>>>>> I need to think a bit more for a better solution.
>>>>>
>>>>> Best regards,
>>>>> Liviu
>>>>>
>>>>>>
>>>>>> Rob
>>>>>>
>>>>>
>>>>
>>>>
>>>> -- 
>>>> Thanks!
>>>> Yijing
>>>>
>>>>
>>>
>>
>>
>> -- 
>> Thanks!
>> Yijing
>>
>> --
>> 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
>>
> 


-- 
Thanks!
Yijing

--
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




[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux