[PATCH 1/7] powerpc: Add mpc8360epb platform support

[Andy Fleming]

On Jun 29, 2006, at 14:56, Vitaly Bordug wrote:

> On Thu, 29 Jun 2006 14:18:51 -0500
> Andy Fleming wrote:
>
>>
>> On Jun 29, 2006, at 13:51, Vitaly Bordug wrote:
>>
>>> On Thu, 29 Jun 2006 13:03:23 -0500
>>> Andy Fleming wrote:
>>>
>>> [snip]
>>>>>>> +	iounmap(bcsr_regs);
>>>>>>> +
>>>>>> And if we have a design, which do not contain real ethernet UCC
>>>>>> usage? Or UCC
>>>>>> geth is disabled somehow explicitly? Stuff like that normally
>>>>>> goes to the
>>>>>> callback that is going to be triggered upon Etherbet init.
>>>>> I will move it.
>>>>
>>>>
>>>> Wait...no.  I don't understand Vitaly's objection.  If someone
>>>> creates a board with an 8360 that doesn't use the UCC ethernet,
>>>> they can create a separate board file.  This is the board-specific
>>>> code, and it is perfectly acceptable for it to reset the PHY like
>>>> this. What ethernet callback could be used?
>>>>
>>>
>>> I am sort of against the unconditional trigger of the ethernet-
>>> specific stuff,
>>> dependless if UCC eth is really wanted in specific configuration.
>>>
>>> For stuff like that I'd make a function (to setup low-level
>>> stuff), and pass it
>>> via platform_info to the eth driver, so that really
>>> driver-specific things happen in driver context only.
>>>
>>> Yes this is board specific file, and virtually everything needed
>>> for the board can take place here.
>>> But usually BCSR acts as a toggle for a several things, and IOW, I
>>> see it more correct to trigger those stuff from the respective
>>> drivers (using a callback passed through platform_info)
>>
>>
>> Callbacks are fairly evil.  And the driver most certainly cannot
>> know about the BCSR, since there may or may not even *be* a BCSR on
>> any given board with a QE.  The PHY only needs to be reset once,
>> during initialization.  On some boards, there is no need to trigger
>> some sort of reset, or enable any PHYs.  I'm still not sure why this
>> should be the domain of the device driver, since it's a board option.
>>
>
> Well. The driver does not need to know anything about bcsr. All it  
> needs to do is to execute the function pointer filled in bsp code,  
> if one exists (If nothing needs to be tweaked in bsp level for a  
> driver, just no need to fill that function pointer). For instance,  
> in PQ2 uart, usb and fcc need to be enabled by bcsr before could be  
> actually utilized, so say fs_enet does all needed upon startup,  
> without messing with board setup code.
> The same does cpm uart...
>
> In case of this particular board, it is not that bad. But I dislike  
> the concept to execute the code in common (for this board) path,  
> not depending if UCC eth disabled in config explicitly.

Well, let me try to see if I understand the two approaches being  
pondered:

1) Use a callback.

Inside the platform info device-specific structure, we create a  
callback.  Something like enet_info->board_init().  The board boots,  
and in the initialization function for that board, the callback is  
assigned to be a function which does the appropriate board-specific  
initialization.  Actually, it makes sure to do this for every device  
which requires such initialization.  Then, later, the devices are  
registered, and matched up with appropriate drivers.  Those drivers  
make sure to invoke enet_info->board_init() before they do anything  
hw related.

2) Let board init code do it

The board boots, and in the initialization function for that board,  
it checks to see if the device exists (by searching the device tree),  
and if so, does any board-specific initialization (in this case,  
configuring the board register to enable the PHY for that device).   
The devices are registered, and matched with appropriate drivers.   
Those drivers operate, blissfully unaware that there was ever any  
danger the board wasn't set up.

Andy