How to generate PWM signal on iMX8ULP?

[wendy-liu]

Dear all,

    I found tpm5 device node in imx8ulp.dtsi, I enable it.

    I chose PTF19 (J20 pin3) to generate PWM signal.

   But I can't fing anything under sysfs,such as /sys/class/tpm or /sys/class/pwm/.I use oscilloscope to measure it waveform , and it keeps outputting a high-level signal.

   My dts ,config, log are as below.

    Hope your reply!Thanks a lot!

Best Regards!

[wendy-liu]

Hello!

Here are some updates  I'd like to share with you.

Fortunately, I enable TPM7 CH5(PTF25) successfully, but there is no output waveform.

my device node  :

+tpm7: tpm@29830000 {
+ //compatible = "fsl,imx8ulp-tpm", "fsl,imx7ulp-tpm";
+ compatible = "fsl,imx7ulp-pwm";
+ reg = <0x29830000 0x10000>;
+ //interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
+ clocks = <&pcc4 IMX8ULP_CLK_TPM7>, <&pcc4 IMX8ULP_CLK_TPM7>;
+ assigned-clocks = <&pcc4 IMX8ULP_CLK_TPM7>;
+ assigned-clock-parents = <&cgc1 IMX8ULP_CLK_FROSC_DIV2>;
+ //assigned-clock-rates = <48000000>;
+ //clock-names = "ipg", "per";
+ status = "okay";
+};

+&tpm7 {
+ pinctrl-names = "default";
+ pinctrl-0 = <&pinctrl_tpm7>;
+ #pwm-cells = <3>;
+};

pinctrl_tpm7: tpm7grp {

                fsl,pins = <

                        MX8ULP_PAD_PTF25__TPM7_CH5      0x2

                >;

};

my commands :

root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8# echo 5 > export
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8# cd pwm5/
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 400000 > period
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 200000 > duty_cycle
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 1 > enable
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5#

[Zhiming_Liu]

Hello,

Do you solve this issue? I just get notification from system, you can add more print in the pwm driver to check if the hardware status.

Best Regards,
Zhiming

[wendy-liu]

yes, I have been solved! Thanks a lot!

[wendy-liu]

Could you test it on iMX8ULP-evk board?

[Zhiming_Liu]

Sure

[wendy-liu]

Looking forward to your reply!Thank you very much!

Best Regards!

[Zhiming_Liu · Accepted solution]

Hello,

Do you solve this issue? I see you have another case about other TPMs clock issue, the TPM clock is generated in ATF: plat/imx/imx8ulp/imx8ulp_bl31_setup.c

	/* config the TPM5 clock */
	mmio_write_32(IMX_PCC3_BASE + 0xd0, 0x92000000);
	mmio_write_32(IMX_PCC3_BASE + 0xd0, 0xd2000000);

Best Regards,
Zhiming

[wendy-liu]

Hello , pwm signal of TPM5 CH0 is successfully generated!

Now , I'm facing another problem...I successfully enable pwm signal of TPM7 CH5(PTF25), but there is no output waveform

tpm7: tpm@29830000 {
//compatible = "fsl,imx8ulp-tpm", "fsl,imx7ulp-tpm";
compatible = "fsl,imx7ulp-pwm";
reg = <0x29830000 0x10000>;
//interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&pcc4 IMX8ULP_CLK_TPM7>, <&pcc4 IMX8ULP_CLK_TPM7>;
assigned-clocks = <&pcc4 IMX8ULP_CLK_TPM7>;
assigned-clock-parents = <&cgc1 IMX8ULP_CLK_FROSC_DIV2>;
//assigned-clock-rates = <48000000>;
//clock-names = "ipg", "per";
status = "okay";
};

&tpm7 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_tpm7>;
#pwm-cells = <3>;
};

pinctrl_tpm7: tpm7grp {
fsl,pins = <
MX8ULP_PAD_PTF25__TPM7_CH5 0x2
>;
};

root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 400000 > period
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 200000 > duty_cycle
root@imx8ulp-lpddr4-evk:/sys/class/pwm/pwmchip8/pwm5# echo 1 > enable

[Zhiming_Liu]

Hello,

The EVK dts also use tpm5 , can you try the 0x57e pinctrl value?

	pinctrl_tpm5: tpm5grp {
		fsl,pins = <
			MX93_PAD_GPIO_IO06__TPM5_CH0		0x57e
		>;
	};

Best Regards,
Zhiming

[wendy-liu]

@Zhiming_Liu 

Thanks for your advice.I tried it, But it doesn't work.......

[Zhiming_Liu]

Hello,

Please comment these two lines and try again.

cs-gpios = <&gpiof 19 GPIO_ACTIVE_LOW>;

MX8ULP_PAD_PTF19__PTF19 0x43

Best Regards,
Zhiming

[wendy-liu]

@Zhiming_Liu 

sorry, i did't see "these two lines".

Could you send me again? I will try it!

[Zhiming_Liu]

updated

[wendy-liu]

sorry, it also did't work

[Zhiming_Liu]

Hello,

1. The default dtsi tpm node is using tpm timer driver and there is no pwm driver using tpm. That's why you can't see the /sys/class/pwm

2.To use pwm tpm driver, you need modify dtsi like this:

			tpm5: tpm@29340000 {
				compatible = "fsl,imx7ulp-pwm";
				reg = <0x29340000 0x1000>;
				// interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
				clocks = <&sosc>, <&sosc>;
				// clock-names = "ipg", "per";
				#pwm-cells = <3>;
				status = "okay";
			};

3. I can see pwm  node after modifing it.

root@imx8ulpevk:/sys/class/pwm/pwmchip0/device/of_node# cat compatible
fsl,imx7ulp-pwmroot@imx8ulpevk:/sys/class/pwm/pwmchip0/device/of_node#

Best Regards,
Zhiming

[wendy-liu]

wow, after modifying it, i can control duty_circle and period under sysfs.

But I measure it waveform , it still keeps outputting a high-level signal.

[Zhiming_Liu]

Hello,

Where is your test point on evk?


Best Regards,
Zhiming

[wendy-liu]

PTF19 (J20 pin3)

pinctrl_tpm5: tpm5grp {
        fsl,pins = <
                 MX8ULP_PAD_PTF19__TPM5_CH0 0x19e
        >;
};

[Zhiming_Liu]

Hello,

The signal from PTF19 is muxed to EPDC_D4 or PTF19_PTF19

Try to include below line in tpm5 node.

pinctrl-assert-gpios = <&pca6416_1 10 GPIO_ACTIVE_LOW>;

Best Regards,
Zhiming

[wendy-liu]

Thanks for your helping!But it still doesn't work(T_T)