topic Re: imx6 spidev cannot set spi_mode (CPOL = 1) in i.MX Processors

imx6 spidev cannot set spi_mode (CPOL = 1)

jongjyhhsieh — Mon, 04 Jun 2018 07:26:54 GMT

I am trying to use mx6q spidev to control a dac chip.

The chip requires CPOL to be enabled so that SCLK is high at idle and starts out with a falling edge.

I have set the SPI_MODE_2(CPOL =1 , CPHA = 0) from user space via ioctrl to the /dev/spidevX.X and was able to read back the same mode from SPI_IOC_RD_MODE. Though when I send spi data, the oscilloscope wave shows that CPOL remains zero at the idle and starts with a rising edge.

Is there any other setting required to change SPI_MODE?

any help would be appreciated.

envrioment:

. imx6q

. linux kernel 3.0.101

. imx_spi, spi_dev

John

Re: imx6 spidev cannot set spi_mode (CPOL = 1)

Carlos_Musich — Mon, 04 Jun 2018 19:29:17 GMT

Hi John,

how are you setting CPOL? If you set CPOL using memtool does it work?

Regards,

Carlos

Re: imx6 spidev cannot set spi_mode (CPOL = 1)

jongjyhhsieh — Thu, 07 Jun 2018 01:49:59 GMT

In the userspace, I open the /dev/spidevX.X and set the mode to be "SPI_MODE_2", which is for CPOL = 1.

After setting, I read the mode back to verified if it is correctly set.

ioctl(fd, SPI_IOC_WR_MODE, &mode)

ioctl(fd, SPI_IOC_RD_MODE, &mode)

I also added some debug code in imx_spi.c and check if the ECSPI register value change and verified that ECSCPI_CONFIGREG 's SCLK_POL bits are correctly set to be idle high.

Re: imx6 spidev cannot set spi_mode (CPOL = 1)

Carlos_Musich — Thu, 07 Jun 2018 15:55:29 GMT

Can you please try setting it with the memtool and let me know if it changes?