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| /openbmc/linux/drivers/dma/ |
| H A D | imx-sdma.c | diff 15f30f513111528c5b0c6185b2bfb7b1a58a6499 Mon Aug 08 07:38:25 CDT 2016 Nandor Han <nandor.han@ge.com> dmaengine: imx-sdma - reduce transfer latency for DMA cyclic clients
Having the SDMA driver use a tasklet for running the clients
callback introduce some issues:
- probability to have desynchronized data because of the
race condition created since the DMA transaction status
is retrieved only when the callback is executed, leaving
plenty of time for transaction status to get altered.
- inter-transfer latency which can leave channels idle.
Move the callback execution, for cyclic channels, to SDMA
interrupt (as advised in `Documentation/dmaengine/provider.txt`)
to (a)reduce the inter-transfer latency and (b) eliminate the
race condition possibility where DMA transaction status might
be changed by the time is read.
The responsibility of the SDMA interrupt latency
is moved to the SDMA clients which case by case should defer
the work to bottom-halves when needed.
Tested-by: Peter Senna Tschudin <peter.senna@collabora.com>
Acked-by: Peter Senna Tschudin <peter.senna@collabora.com>
Reviewed-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Nandor Han <nandor.han@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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