[PATCH v3 0/4] Add DMA support for ti_am335x_adc driver

From: Mugunthan V N
Date: Wed Oct 05 2016 - 05:07:34 EST

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
* 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(-)