Flat device tree definitions for FLASH and MTD partitioning

[Wolfgang Grandegger]

Sergei Shtylyov wrote:
> Hello.
> 
> Wolfgang Grandegger wrote:
> 
>>>>>>> are there already some thought or even example code on how to 
>>>>>>> define Flash memory and MTD partitions in the DTS. This would 
>>>>>>> avoid the ackward MTD partitioning via static structure or boot 
>>>>>>> line argument and could be done in a generic way.
> 
>>>>>>     See Documentation/powerpc/booting-without-of.txt and 
>>>>>> drivers/mtd/physmap_of.c for what's been already done.
> 
>>>>>    I meant drivers/mtd/maps/physmap_of.c
> 
>>>> I had a closer look to this driver. Unfortunately, it can not handle 
>>>> yet  multiple FLASH banks. This could be achieved with an additional 
>>>> property "bank_count". What do you think?
> 
>   Please use hyphen, not underscore in property names ("device_type" 
> seems an only exception from this rule).

Yes, I know and I also wondered why an "_" is used for the device type.

>>>  I'm not sure what banks you're talking about -- note that this 
>>> driver is equivalen in functionality to the plain 'physmap' driver 
>>> and there's inherited "bank-width" property that handles flash banking.
> 
>> Yes, I know. Nevertheless the driver cannot handle flash regions 
>> composed of more than on FLASH bank because we need to probe every 
>> bank. Search for "BANK" in drivers/mtd/maps" to understand what I mean.
> 
>   Hm, from what I could see, those banks are separate maps registered to 
> MTD subsys separately.
> What's the point of adding a count property when we simply can define 
> multiple "rom" devices?

To complete this thread, physmap_of can map _one_ FLASH region composed 
of one or more FLASH banks. But it currently cannot map more than _one_ 
FLASH region. It would be nice to extend it for multiple FLASH 
definitions (could code it when time permits).

Wolfgang.