dmaengine: rcar-dmac: Priority and slow mode prototypes [PATCH 1/3] dmaengine: rcar-dmac: Priority handling prototype [PATCH 2/3] dmaengine: rcar-dmac: Slow mode prototype [PATCH 3/3] arm64: dts: r8a7795: Use slow mode for TX on SCIF2/DEBUG1 This series implements prototype support for priority handling and slow mode for the rcar-dmac driver and in particular the SYS-DMAC hardware found on several R-Car devices. The priority handling uses MID/RID values to determine if channels below to RX or TX sides. The case of RX is unchanged and as low channel number as possible is used to ensure high priority. New with patch 1/3 is that TX is allocated with highest channel number first to force low priority. Some ugly layer violations are implemented to keep track of which channels that are in use and which that are free. The slow mode simply extends the MID/RID value to allow encoding a 4-bit value in bit 8-11 to specify the SLM bit value. With this value set the channel associated with the device will be processed slower. The idea is that the slow mode can be used for testing to force underruns to harden other parts of the system. The third patch shows how to make use of the second patch These patches probably need a bit more effort to be beaten into shape for upstream merge. So simply treat these as experimental test code. Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@xxxxxxxxxxxxx> --- Developed on top of renesas-drivers-2017-02-21-v4.10 arch/arm64/boot/dts/renesas/r8a7795.dtsi | 2 drivers/dma/sh/rcar-dmac.c | 109 +++++++++++++++++++++++++++--- 2 files changed, 101 insertions(+), 10 deletions(-)
