From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Hellstrom <thellstrom@vmware.com>
Subject: Use of pci_map_page in nouveau, radeon TTM.
Date: Tue, 01 Oct 2013 12:16:16 +0200
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To: Jerome Glisse <jglisse@redhat.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Jerome, Konrad

Forgive an ignorant question, but it appears like both Nouveau and 
Radeon may use pci_map_page() when populating TTMs on
pages obtained using the ordinary (not DMA pool). These pages will, if I 
understand things correctly, not be pages allocated with
DMA_ALLOC_COHERENT.

 From what I understand, at least for the corresponding dma_map_page() 
it's illegal for the CPU to access these pages without calling
dma_sync_xx_for_cpu(). And before the device is allowed to access them 
again, you need to call dma_sync_xx_for_device().
So mapping for PCI really invalidates the TTM interleaved CPU / device 
access model.

Or did I miss something here?

Thanks,
Thomas