Subject: Re: [PATCH 2/2] pci: Use Qemu created PCI device nodes

From: Nikunj A Dadhania <[email-masked]>
Date: Mon, 27 Apr 2015 10:17:39 +0530

Hi Thomas,

Thomas Huth <[email-masked]> writes:
>  Hi Nikunj,
>
> On Wed, 22 Apr 2015 16:27:20 +0530
> Nikunj A Dadhania <[email-masked]> wrote:
>
>> PCI Enumeration has been part of SLOF. Now with hotplug code addition
>> in Qemu, it makes more sense to have this code a one place, i.e. Qemu.
>
> s/Qemu/QEMU/ and s/code a one place/code in one place/ ?

Sure

>
>> Adding routines to walk through the device nodes created by Qemu. SLOF
>> will configure the device/bridges and program the BARs for
>> communicating with the devices.
>
> I wonder whether it would make more sense to also set up the BARs etc.
> in QEMU instead of SLOF?
>
>> 
>> diff --git a/board-qemu/slof/pci-phb.fs b/board-qemu/slof/pci-phb.fs
>> index e307d95..30b7443 100644
>> --- a/board-qemu/slof/pci-phb.fs
>> +++ b/board-qemu/slof/pci-phb.fs
>> @@ -283,6 +283,41 @@ setup-puid
>>     THEN
>>  ;
>>  
>> +: phb-pci-walk-bridge ( -- )
>> +    phb-debug? IF ."   Calling pci-walk-bridge " pwd cr THEN
>> +
>> +    get-node child ?dup 0= IF EXIT THEN    \ get and check if we have children
>> +    BEGIN
>> +        dup                           \ Continue as long as there are children
>> +    WHILE
>
> Most Forth code uses the same indentation for the code between
> BEGIN...WHILE and WHILE...REPEAT ... so I think you could decrease the
> indentation of the following block by one level.

Sure, emacs is autoindenting this, so i ended up like this.

>
>> +            \ Set child node as current node:
>> +            dup set-node
>
> Below you are calling pci-device-setup which in turn might include some
> pci-class_*.fs or pci-device_*.fs files (or even run some FCODE?). At
> least pci-class_02.fs seems to use an INSTANCE VARIABLE, i.e. the
> instance template should get modified in that case ==> Please
> double-check whether you need to use extend-device here instead (I'm
> not 100% sure right now ... what happens
> for example when you run qemu with a network device that SLOF does not
> provide a pci-device_*.fs for? I guess it will try to include
> pci-class_02.fs and fail due to the INSTANCE VARIABLE ?)

I tried using rtl8139 device, SLOF does not provide driver for that. And
that did not create any problem.

Not sure about FCODE though, i will do more experiments with non
supported devices to check if things are fine. 

>
>> +            my-space pci-set-slot       \ set the slot bit
>
> pci-set-slot seems to rely on the pci-device-slots global variable.
> This is normally initialized by pci-probe-bus. Now that you provide
> your own implementation of that function below, I think it should
> likely also set up the pci-device-slots variable, shouldn't it?

Yes, I will need to initialize it for every bus probe to 0.

>
>> +            my-space pci-htype@         \ read HEADER-Type
>> +            7f and                      \ Mask bit 7 - multifunction device
>> +            CASE
>> +               0 OF my-space pci-device-setup ENDOF  \ | set up the device
>> +               1 OF my-space pci-bridge-setup ENDOF  \ | set up the bridge
>> +               dup OF my-space pci-htype@ pci-out ENDOF
>> +           ENDCASE
>> +           peer
>> +    REPEAT drop
>> +    get-parent set-node
>> +;
>
> The remaining part of the patch looks ok to me.

Regards,
Nikunj