> On 4. 10. 2023, at 15:32, Martin Povišer <povik+lin@xxxxxxxxxxx> wrote: > > > Hello Vinod, > > some of those things we have discussed on v1 already, let me link > that here: > https://lore.kernel.org/asahi/20230712133806.4450-1-povik+lin@xxxxxxxxxxx/T/#t > > Anyway find my replies below. > > Best regards, Martin > >> On 4. 10. 2023, at 15:12, Vinod Koul <vkoul@xxxxxxxxxx> wrote: >> >> On 28-08-23, 19:00, Martin Povišer wrote: >>> Add a dmaengine driver for the Apple SIO coprocessor found on Apple >>> SoCs where it provides DMA services. Have the driver support cyclic >>> transactions so that ALSA drivers can rely on it in audio output to >>> HDMI and DisplayPort. >>> >>> Signed-off-by: Martin Povišer <povik+lin@xxxxxxxxxxx> >>> --- >>> MAINTAINERS | 2 + >>> drivers/dma/Kconfig | 11 + >>> drivers/dma/Makefile | 1 + >>> drivers/dma/apple-sio.c | 868 ++++++++++++++++++++++++++++++++++++++++ >>> 4 files changed, 882 insertions(+) >>> create mode 100644 drivers/dma/apple-sio.c ... >>> +/* >>> + * There are two kinds of 'transaction descriptors' in play here. >>> + * >>> + * There's the struct sio_tx, and the struct dma_async_tx_descriptor embedded >>> + * inside, which jointly represent a transaction to the dmaengine subsystem. >>> + * At this time we only support those transactions to be cyclic. >>> + * >>> + * Then there are the coprocessor descriptors, which is what the coprocessor >>> + * knows and understands. These don't seem to have a cyclic regime, so we can't >>> + * map the dmaengine transaction on an exact coprocessor counterpart. Instead >>> + * we continually queue up many coprocessor descriptors to implement a cyclic >>> + * transaction. >>> + * >>> + * The number below is the maximum of how far ahead (how many) coprocessor >>> + * descriptors we should be queuing up, per channel, for a cyclic transaction. >>> + * Basically it's a made-up number. >>> + */ >>> +#define SIO_MAX_NINFLIGHT 4 >> >> you meant SIO_MAX_INFLIGHT if not what is NINFLIGHT? > > I mean the number is arbitrary, it doesn’t reflect any coprocessor limit since > I haven’t run the tests to figure one out. It's supposed to be a small reasonable > number. Ah I didn’t get what you were commenting on at first. Sure, INFLIGHT, NINFLIGHT, it’s the same thing to me. I have a tendency to put in the N to signify it’s the “number of”. Best, Martin
