Introudce fallback pio way at spi core level so that the tx/rx buffer mapped by spi core for dma could be unmap and fallback pio again. Hence no need the below patch where 'dma_sync_sg_for_devic' to sync fresh data back into 'device' memory and sync to 'cpu' again in spi core. https://www.spinics.net/lists/arm-kernel/msg812236.html
If you want to use this fallback feature, please set 'master->flags' with SPI_MASTER_FALLBACK and add 'master->fallback' checking in your can_dma() to ensure it can fallback to pio. Robin Gong (2): spi: introduce fallback to pio spi: spi-imx: add fallback feature drivers/spi/spi-imx.c | 23 +++++------------------ drivers/spi/spi.c | 11 +++++++++++ include/linux/spi/spi.h | 4 ++++ 3 files changed, 20 insertions(+), 18 deletions(-) -- 2.7.4
