[alsa-devel] Problem to init AD1938 on i.MX25

Sascha Hauer s.hauer at pengutronix.de
Mon Aug 16 09:30:40 CEST 2010

Hello Sven,

On Mon, Aug 16, 2010 at 06:51:17AM +0200, Sven Zeisberg wrote:
>   Hello,
> we're working on an ALSA  driver for AD1938 for i.MX25 based system.
> On the I²S the CODEC is Master. On the SPI, the MCU is Master.
> SSI seems to work (when we set the CODEC as Master by Hardware).
> We have problems to get the communication via SPI working. The CODEC 
> requires 24Bit words and we can set SPI according to this in the 
> board-file and verify this also with a logic analyzer. However, we can 
> send only one word to the CODEC! This first word is transferred 
> correctly, but all subsequent transfers show no activity on the SPI 
> lines. We do not get any error messages from the SPI drivers! All SPI 
> writes after the first word seem to be executed in software but show not 
> effect in hardware. All reads return 0xff.

This is probaly more a problem in the SPI driver than alsa related. The
i.MX SPI unit comes in many different variants and there may well be a
bug in the i.MX25 path. As a test you could configure the SPI pads in
gpio mode and use the bitbang gpio spi driver (drivers/spi/spi_gpio.c).
When this works you can hunt down the bug in the SPI driver.


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