[PATCH 6/7] OMAP3: board-dt: Add generic board file for DT support

[Cousson, Benoit]

On 9/2/2011 1:57 PM, Tony Lindgren wrote:
> * Cousson, Benoit<b-cousson at ti.com>  [110902 14:10]:
>> On 9/2/2011 12:43 PM, Tony Lindgren wrote:
>>> * Cousson, Benoit<b-cousson at ti.com>   [110902 11:13]:
>>>> Hi Tony,
>>>>
>>>> On 9/2/2011 10:09 AM, Tony Lindgren wrote:
>>>>> Hi,
>>>>>
>>>>> * Benoit Cousson<b-cousson at ti.com>    [110901 19:52]:
>>>>>> Create an OMAP3 generic board to start the DT migration.
>>>>>
>>>>> I don't think this needs to be SoC specific, we can add multiple
>>>>> DT_MACHINE_START entries into a single file. So it should be
>>>>> just board-omap-dt.c.
>>>>
>>>> I do agree, it should not, I made that comment into the
>>>> board-omap4-dt.c, but for the moment we still have dedicated OMAP
>>>> specifics stuff at board level, like the map_io.
>>>
>>> Well map_io can also be set in DT_MACHINE_START. For most part
>>> it already is generic like omap3_map_io and omap4_map_io.
>>> So that should not stop anything.
>>
>> OK, I think I was trying to be a little bit more extreme, meaning only one omap_map_io for every OMAPs.
>> Then, inside omap_map_io we can use the DT compatible information to retrieve the proper OMAPs revision and thus use the proper init table.
>>
>> Whereas in your case you are still relying on the various DT_MACHINE entries to detect which OMAP revision is used.
>
> Sure that can be changed. But why not get the whole data that's
> now in various structs from DT too? It's just something like:
>
>          .class  = OMAP243X_CLASS,
>          .tap    = OMAP2_L4_IO_ADDRESS(0x4900a000),

BTW, how can we get rid of that OMAP2_L4_IO_ADDRESS?

>          .sdrc   = OMAP243X_SDRC_BASE,
>          .sms    = OMAP243X_SMS_BASE,
>          .ctrl   = OMAP243X_CTRL_BASE,
>          .prm    = OMAP2430_PRM_BASE,
>          .cm     = OMAP2430_CM_BASE,
>
> And all these could be just defined in DT right?

Hehe, it is just a phase-one-proof-of-concept... the phase two was 
supposed to move that to DT. But for the moment, I was trying to have a 
more conservative approach using the existing data like for hwmod.

The other point is that we still have to deal with the FDT at that 
point, the DT is not yest available that why I didn't extract too many 
informations from the FDT.
Moreover, in theory, these informations will not be mixed like today, 
but will be in their own relevant DT nodes, somewhere inside the tree.
Bottomline... it was a little bit more tricky.

>> It looks to me that relying on several DT_MACHINE_START to identify a SoC version is a little bit more a hack.
>> I will let the device-tree experts answering that question :-)
>> For my point of view, using DT compatible in the various place where the OMAP revision is important, might allow a finer granularity.
>
> Sure I agree.
>
>>>> I have an other series that make the map_io DT aware to get rid of
>>>> that, but it still not finalized.
>>>
>>> Hmm maybe take a look again? We've already sorted out quite a bit
>>> of the init stuff over past few merge windows. If there's still
>>> something blocking that, let's clear it out ASAP.
>>
>> Now that I understand your approach, it is fine. Please find below an example of what I was trying to achieve, and why that point was an issue.
>> The clear advantage of your method is that not further effort will be require for this part. At least for the moment.
>
> Well I guess the globals could come from device tree still :)

Fully agree. It just needs some more time :-)

> In general, I'd like to get rid of the cpu_is_omapxxxx stuff
> and SoC detection early as that always requires DEBUG_LL to
> see any decent debug info when things go wrong.
>
> If we get the SoC major type from DT, then we only need to
> do SoC specific ES revision and GP/HS omap detection. And that's
> very simple code compared to the current cpu_is_omapxxxx stuff.

In fact only the tap should be required at map_io time to get the 
DEVICE_ID, I guess that the others entries could be retrieve later?

           .sdrc   = OMAP243X_SDRC_BASE,
           .sms    = OMAP243X_SMS_BASE,
           .ctrl   = OMAP243X_CTRL_BASE,
           .prm    = OMAP2430_PRM_BASE,
           .cm     = OMAP2430_CM_BASE,

If this is the case, we can then add a DEVICE_ID address entry in DT 
root to be retrieved easily with the FDT.

> Then we can boot with the DT information pretty far to map_io
> and initialize low-level serial console, and then set up things
> further while having a decent console ;)

Yeah! The holy grail.

Benoit