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.
Sascha