From: Mathias Nyman
> Sent: 11 May 2017 15:45
> 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.
Ah, ok, so if the physical address is too large a separate bounce
buffer is used?
David
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
