How to handle named resources with DT?
Paul Walmsley
paul at pwsan.com
Mon Aug 29 11:57:35 EST 2011
Hi,
one case that I forgot to mention:
On Sun, 28 Aug 2011, Paul Walmsley wrote:
> Several upstream device drivers get their DMA request line IDs from the
> device data format[14][15][16]. But more drivers should be doing this
> than currently are[17]:
>
> - the device driver author may have hardcoded the DMA request line ID,
> assuming it would never change
>
> - DMA could be broken on the device due to hardware bugs, so it is unused
>
> - the driver author may just never have gotten around to implementing DMA,
> or was reassigned to another project, or couldn't figure it out
>
> - the device may have its own internal DMA controller logic, so support
> for an external DMA controller was simply never added
- the driver may be using software-initiated DMA, which doesn't use a
DMA request line, nor does it rely on the device to start or stop DMA.
Instead, the CPU reprograms the DMA controller when the driver receives
an interrupt
- Paul
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