How to Set SPI's Clock

[jiehunt]

I use the imx6ql-sabreauto board to communicate with a slave board.

I want to know the highest speed of spi block.

I read the document and i think the highest speed is up to 60MHz.

and i use the ioctl like this

 ioctl (fd, SPI_IOC_WR_MAX_SPEED_HZ, 60MHz)

But , I don't confirm whether this is effective or not.

How do I know the actual speed of the SPI work with?

Thank you!

[igorpadykov · Accepted solution]

Hi Jie

max. ecspi frequency can be found in sect.4.11.2 ECSPI Timing Parameters

i.MX6DQ Datasheet

http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6DQCEC.pdf

example of usage with spi-nor flash using dts "spi-max-frequency" parameter in

imx6qdl-sabresd.dtsi

linux-2.6-imx.git - Freescale i.MX Linux Tree 

Best regards
igor
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[jiehunt]

Thank you for your answer.

Actually my imx6qdl-sabreauto.dtsi is like this:

&ecspi1{
  fsl,spi-num-chipselects = <1>;
  cs-gpios = <&gpio5 25 0>;
  pinctrl-names = "default";
  pinctrl-0 = <&pinctrl_ecspi1>;
  status = "okay";
  spidev0: spi@0 {
  compatible = "spidev";
  spi-max-frequency = <40000000>;
  reg = <0>;
  };
};

So, I think the SPI is work with 40MHz.