[Forum] Try only to realise the truth | ANN.lu |
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Try only to realise the truth : Comment 240 of 335 | ANN.lu |
Posted by Ferry on 06-Jul-2004 11:15 GMT | In reply to Comment 235 (Johan Rönnblom): "Ferran, it's possible to do the exact same in Linux."
If I understood Chris explanation correctly, where he says the ArticiaS does not flag accessed memory as "dirty", therefore the CPU does not automatically know, that it has to update/flush its caches, Linux expects Articia to change that flag, but Articia doesn't do, so DMA transfers fail. I'm not an expert, but it seems not a case of 'non-coherent DMA' as Ben
Herrenschmidt says, it seems that Linux drivers are simply not "synced" with Articia specs. To make it work, this "software flag switch" should be implemented for when Linux detects it's running in a Articia equipped board. Does it worth the effort? I don't know, but that's another question...
As for OS4, and as Chris says If all drivers are written with this manual software cache coherence in mind, this is no problem, and that's precisely the way it is being done, AFAIK.
Saluditos,
Ferrán. |
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