imx8mm pwm in uboot not work

[sclu]

My lcd backlight need pwm control, so I config pwm4, backlight in dts:

lvds_backlight: lvds_backlight {
compatible = "pwm-backlight";
pwms = <&pwm4 0 100000 0>;
status = "okay";
enable-gpios = <&gpio4 26 GPIO_ACTIVE_HIGH>;

brightness-levels = < 0 1 2 3 4 5 6 7 8 9
.......
};

&pwm4 {
#pwm-cells = <3>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_pwm4>;
status = "okay";
};

I also open the driver: pwm-imx.c pwm-backlight.c in Config file

But it got stuck in the driver:

int pwm_config_internal(struct pwm_regs *pwm, unsigned long period_cycles,

unsigned long duty_cycles, unsigned long prescale)

{

u32 cr;

    printf("%s %d, &pwm->ir=0x%x\n", __func__, __LINE__, &pwm->ir);

writel(0, &pwm->ir);

    printf("%s %d\n", __func__, __LINE__);

cr = PWMCR_PRESCALER(prescale) |

PWMCR_DOZEEN | PWMCR_WAITEN |

PWMCR_DBGEN | PWMCR_CLKSRC_IPG_HIGH;

    printf("%s %d\n", __func__, __LINE__);

writel(cr, &pwm->cr);

    printf("%s %d\n", __func__, __LINE__);

/* set duty cycles */

writel(duty_cycles, &pwm->sar);

    printf("%s %d\n", __func__, __LINE__);

/* set period cycles */

writel(period_cycles, &pwm->pr);

    printf("%s %d\n", __func__, __LINE__);

return 0;

}

The log show the "&pwm->ir"  address is correct: 0x30690008, But it's stuck here :

writel(0, &pwm->ir);

It seems that the address 0x30690008 cannot be directly accessed

I have also tried using ioremap function to obtain addresses, But there is a compilation error prompt

I have also tried to disable the PWM4 configuration in DTS, and used:

  pwm_init(3, 0, 0);

  pwm_config(3, 5, 10);

  pwm_enable(3);

But we also encountered the same problem

Can someone help me please ?

[Dhruvit]

Hi @sclu,

I hope you are doing well.

Please confirm if you were able to read/write the memory from the Uboot command or not.

Kindly refer to the below files for the device tree configuration for PWM in the U-boot.

doc/device-tree-bindings/pwm.

Kindly share the whole device tree file and the log you are getting in case of failure to further debug the issue.

Thanks & Regards,

Dhruvit Vasavada

[sclu]

Thank you for your reply, My driver is attached.

I use the md.l command, and the system hang up:

[Dhruvit · Accepted solution]

Hi @sclu,

I hope you are doing well.

system hang-up is caused due to clock not being enabled for the PWM module.

PWM support for i.MX8M Processors is not available in the uboot version before v2022.04.

PWM  DM support & register support is added using the below commits in v2023.04.

arch: mach-imx: imx8m: add pwm_regs struct in imx-regs

arch: mach-imx: imx8m: add pwm ctrl registers fields defines

One can refer to the below-mentioned link to add pwm support in imx8m.

https://cuteparrot.pixnet.net/blog/post/229123814-%5Bnxp%5D%5Bimx8mm%5Dhow-to-enable-pwm1-on-uboot

Thanks & Regards,
Dhruvit Vasavada

[sclu]

Your answer perfectly solved all my problems，I add:
clock_enable(CCGR_PWM4,0);
clock_set_target_val(PWM4_CLK_ROOT, CLK_ROOT_ON |
CLK_ROOT_SOURCE_SEL(0)| CLK_ROOT_POST_DIV(CLK_ROOT_POST_DIV1));
clock_enable(CCGR_PWM4, 1);
Use my code and it will work!