i.MX6 DMA and ADC

[strahinjavukovi]

We are using i.MX6UL processor and we need to have fast sapling of one ADC channel.

Since driver is not supporting DMA transfer vf60_adc, my idea was to implement IIO buffer and Dmaengine into the driver.

SDMA is responsigle for communication between memory and peripherals, but I never saw that DMA was used for ADC transfer.

Does sdma-imx6q.bin (script) supports this type of transfer or additional script should be written?

From device tree documentation, I think that this is not possible:

Linux/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt - Linux Cross Reference - Free Electron... 

In case that is necessary to write new script, is there a free version of CodeWarrior and source code of dma-imx6q.bin binary?

p.s. I found some similar questions regardins SDMA:

Custom SDMA script to convert bayer image 

[igorpadykov]

Hi Strahinja

you are right, linux sdma supports limited number peripherals which are described on linux documentation on

http://www.nxp.com/products/software-and-tools/software-development-tools/i.mx-software-and-tools/i....

General approach for writing new script and adding sdma support for new peripheral is using Professional Services:

http://www.nxp.com/support/nxp-professional-services:PROFESSIONAL-SERVICE

Unfortunately source code of dma-imx6q.bin is not available, sorry.

Best regards
igor
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[strahinjavukovi]

Hello Igor

since you confirmed that SDMA can`t perform ADC transfer, is it possible to do this using APBH-Bridge-DMA?

I know that this DMA is used for NAND, but for what other peripherals can be used? In reference maunal is written "memory-mapped I/O to the APB device", but I am not certain what that means. Can you clarify this for me?

Best regards

Strahinja

[igorpadykov]

Hi Strahinja

I am afraid it can not be used. SDMA works with particular

module on specific bus (to which that peripheral connected), one

can look at Figure 43-1. SDMA Block Diagram i.MX6UL Reference Manual

http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6ULRM.pdf

Very simplified, there are three buses: spba, burst dma, peripheral dma,

which have some number of connected peripherals. Each group is handled

by own script. Better sdma description is given in Table A-1. SDMA Scripts Overview

i.MX53 RM, so one can find for example two uart different scripts: Shared UART and UART.

One is connected on spba, other on peripheral dma. NAND is connected to own APBH-Bridge-DMA bus.

Also may be useful to check

Freescale i.MX SDMA tutorial (part I) 

Best regards
igor

[strahinjavukovi]

Hello Igor,

since our main goal is to have fast sampling, we can maybe use external ADC with SPI interface.

Problem is that from i.MX6UL and i.MX53 RM I don´t see that SDMA has a support for SPI.

From the other hand in Linux device tree documentation is written CSPI support (ID 7 and 8):

Linux/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt - Linux Cross Reference - Free Electron... 

So I am confused, does current bin support SPI or not?

Best regards

Strahinja

[igorpadykov]

Hi Strahinja

for i.mx there are many bsps, please check for example

https://community.freescale.com/message/402940#402940

official nxp releases do not support spi sdma, please check 

Linux Manual Chapter 4 Smart Direct Memory Access (SDMA)

included in doc package on link

i.MX 6 / i.MX 7 Series Software and Development Tool|NXP 

Best regards
igor