On Fri, Feb 01, 2019 at 09:07:45AM -0800, Sowjanya Komatineni wrote: > This patch adds DMA support for Tegra I2C. > > Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for > transfer size of the max FIFO depth and DMA mode is used for > transfer size higher than max FIFO depth to save CPU overhead. > > PIO mode needs full intervention of CPU to fill or empty FIFO's > and also need to service multiple data requests interrupt for the > same transaction. This adds delay between data bytes of the same > transfer when CPU is fully loaded and some slave devices has > internal timeout for no bus activity and stops transaction to > avoid bus hang. DMA mode is helpful in such cases. > > DMA mode is also helpful for Large transfers during downloading or > uploading FW over I2C to some external devices. > > Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx> > --- > [V9] : Rebased to 5.0-rc4 > Removed dependency of APB DMA in Kconfig and added conditional check > in I2C driver to decide on using DMA mode. > Changed back the allocation of dma buffer during i2c probe. > Fixed FIFO triggers depending on DMA Vs PIO. > [V8] : Moved back dma init to i2c probe, removed ALL_PACKETS_XFER_COMPLETE > interrupt and using PACKETS_XFER_COMPLETE interrupt only and some > other fixes > Updated Kconfig for APB_DMA dependency > [V7] : Same as V6 > [V6] : Updated for proper buffer allocation/freeing, channel release. > Updated to use exact xfer size for syncing dma buffer. > [V5] : Same as V4 > [V4] : Updated to allocate DMA buffer only when DMA mode. > Updated to fall back to PIO mode when DMA channel request or > buffer allocation fails. > [V3] : Updated without additional buffer allocation. > [V2] : Updated based on V1 review feedback along with code cleanup for > proper implementation of DMA. > > drivers/i2c/busses/i2c-tegra.c | 368 +++++++++++++++++++++++++++++++++++++---- > 1 file changed, 335 insertions(+), 33 deletions(-) With Dmitry's concern addressed: Acked-by: Thierry Reding <treding@xxxxxxxxxx>
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