On 07/10/2012 03:12 PM, Marek Vasut wrote:
Dear Wolfgang Denk,
Dear Michal Simek,
In message4FFC1EF8.9060705@monstr.eu you wrote:
The hardest part I have identify on microblaze was about u-boot variables. Because based on information from device-tree you can choose where variables should be stored and also this memory should be accessible before u-boot try to read variables. It mean in very early state.
Device initialization before relocation is already hard enough;
+1
resources are very limited then.
And we'll be introducing the early mallocator. This is where MPC85x will blow my mind :) (I'm repeating myself here, but it might help getting others unaware of the DM work better in line).
You will add the additional need to have the FDT library available then, too. Not to mention that you need to load the DT blob, too.
DT blob can be read from ROM if that was the problem. The DT library and parser might be an issue.
This will be a lot of added complexity.
And therefore slowing down the boot. But I believe it can be optimized to leverage this to some point. Though I'm not quite sure how much. This is worthy investigation.
Michal, can you try investigating how will the DT probing intertwine with the DM?
Firstly I need to understand what you are trying to achieve and how. Then if I have time I can look at how DT probing can be added to it.
But I think that there is good example in the Linux kernel how to do it. I believe that device-tree guys will have some good comments and experiences from the kernel.
Thanks, Michal