On 09.05.2017 18:38, David Laight wrote:
From: Mathias Nyman
Sent: 09 May 2017 12:24
On 08.05.2017 09:26, Mathias Nyman wrote:
On 05.05.2017 15:05, Matthias Lange wrote:
There is no reason to restrict allocations to the first 16MB ISA DMA
addresses.
...
What about the 4G boundary?
Can you elaborate on when this 4G boundary is an issue?
Driver set dma mask (64 or 32), uses kmalloc() to get kernel logical addresses and
then dma_map_single to map it.
IIRC dma_alloc_coherent() is most likely what the code should be using.
These bounce buffer is small, per endpoint and only lives for the time of the endpoint.
We know the direction of the data, and exactly when trb is done (syncpoint).
the bounce buffer is used and mapped only when the data we want transferred breaks a
xHC boundary requirement, and unmapped immediately when the transfer is done.
I think streaming fits better this purpose.
-Mathias
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