Enable clkout1 on AM437x through software

Trent Oshiro

We need to enable clkout1 on the AM437x because we have a device that depends on that clock output. I was told from a TI rep already that we only need to activate clkout1 through SYSBOOT17 if we are booting from ROM (which we're not), otherwise, we can enable it from the bootloader. My questions is how do we enable it from the bootloader? If we are working with the TI AM437x EVM SDK, what exactly do we need to change? We have already tried adding the following lines in the .dts file to no avail:

pinctrl-0 = <&clkout1_pin &clkout2_pin &ddr3_vtt_toggle_default &wlan_pins_default>;
pinctrl-1 = <&clkout1_pin &clkout2_pin &ddr3_vtt_toggle_default &wlan_pins_sleep>;

clkout1_pin: clkout1_pin {
pinctrl-single,pins = <
0x270 (PIN_OUTPUT_PULLUP | MUX_MODE3)
>;
};

The way we have tested to see if the clock is outputting or not, we have been probing for our device on the I2C rail. We have already confirmed that when the clock is not outputting anything, the I2C probe returns nothing. But when we enabled the clock through SYSBOOT17, the I2C probe returned the device's address.

Thanks,

Trent

over 10 years ago

0 Evan W over 10 years ago

TI__Mastermind 39960 points

Trent,

Have you looked at the PRCM_CM_CLKOUT1_CTRL Register? Please refer to page 439 of the Technical Reference Manual for the AM437x device: www.ti.com/.../spruhl7c.pdf

On this page, you can note that bit 23 is associated with the CLKOUT1EN which determines if the CLKOUT is enabled. From there you can decide on selecting divisions. I'm not sure that this is the final answer to your question, but it is a starting place.

Thanks,
Evan

0 Trent Oshiro over 10 years ago in reply to Evan W

Intellectual 505 points

Evan,

We actually did already try setting bit 23 of the PRCM_CM_CLKOUT1_CTRL register as well. We set bit 23 to 1 and all other bits to 0, and verified through our own debug messages that bit 23 was indeed being set to 1. We were still not able to get the I2C probe to recognize our device. Is there something we're missing?

Thanks,
Trent

0 Trent Oshiro over 10 years ago in reply to Trent Oshiro

Intellectual 505 points

Assuming we did not set that register bit correctly, how are we supposed to set that bit? What file(s) do we have to modify?

0 Steve Kipisz over 10 years ago in reply to Trent Oshiro

TI__Genius 15510 points

Actually, you are booting from ROM. The AM437x has a boot ROM that reads the sysboot pins at power up to determine how to boot and any other settings. sysboot17 enables or disables clkout1. Pulling that up should enable clkout1.

Steve K.

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Enable clkout1 on AM437x through software