The ADC has a 64 word depth fifo length which holds the ADC data till the CPU reads. So when a user program needs a large ADC data to operate on, then it has to do multiple reads to get its buffer. Currently if the application asks for 4 samples per channel with all 8 channels are enabled, kernel can provide only 3 samples per channel when all 8 channels are enabled (logs at [1]). So with DMA support user can request for large number of samples at a time (logs at [1]). Tested the patch on AM437x-gp-evm and AM335x Boneblack with the patch [2] to enable ADC and pushed a branch for testing [3] Changes from v2: * Fixed an issue on handling of error return from dma_request_chan(). Changes from Initial version: * Changed DMA api from dma_request_slave_channel_compat() to dma_request_chan() * Changed variable names to have more clear information as per comments from Peter. [1] - http://pastebin.ubuntu.com/23278405/ [2] - http://pastebin.ubuntu.com/23211494/ [3] - git://git.ti.com/~mugunthanvnm/ti-linux-kernel/linux.git iio-dma-v2 Mugunthan V N (4): mfd: ti_am335x_tscadc: store physical address drivers: iio: ti_am335x_adc: add dma support ARM: dts: am33xx: add DMA properties for tscadc ARM: dts: am4372: add DMA properties for tscadc arch/arm/boot/dts/am33xx.dtsi | 2 + arch/arm/boot/dts/am4372.dtsi | 2 + drivers/iio/adc/ti_am335x_adc.c | 148 ++++++++++++++++++++++++++++++++++- drivers/mfd/ti_am335x_tscadc.c | 1 + include/linux/mfd/ti_am335x_tscadc.h | 8 ++ 5 files changed, 158 insertions(+), 3 deletions(-) -- 2.10.0.372.g6fe1b14 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
