i.mx 8ULP PWM on M33 core via SRTM/RPMSG from Linux

[niclas_karlsson]

I have backlight connected to the PWM on the M33, PTC1 (TMP2_CH0). My understanding is that I can modify the device tree for Linux, running on the A35, to use rpmsg to control the PWM. That would allow me to control the backlight with the sysfs as normally.

How do I choose which TMP that shall be used? I couldn't find that information in the documentation.
My device tree has these entries for the backlight and PWM:

pwm_backlight: backlight {
    compatible = "pwm-backlight";
    pwms = <&tpm_rpchip_0 0 1000000 0>;
    brightness-levels = < 0  1  2  3  4  5  6  7  8  9
             10 11 12 13 14 15 16 17 18 19
             20 21 22 23 24 25 26 27 28 29
             30 31 32 33 34 35 36 37 38 39
             40 41 42 43 44 45 46 47 48 49
             50 51 52 53 54 55 56 57 58 59
             60 61 62 63 64 65 66 67 68 69
             70 71 72 73 74 75 76 77 78 79
             80 81 82 83 84 85 86 87 88 89
             90 91 92 93 94 95 96 97 98 99
            100>;
    default-brightness-level = <100>;
    default-enable = <0>;
    status = "okay";
  };
};

&tpm_rpchip_0 {
  status = "okay";
};

And int the file imx8ulp-rpmsg.dtsi:

  tpm_rpchip_0: pwm {
    compatible = "fsl,pwm-rpchip";
    #pwm-cells = <3>;
    fsl,pwm-channel-number = <6>;
    status = "disabled";
  };

Thanks for the help!

[jimmychan]

The alias in imx8ulp-rpmsg.dtsi decide which instance is used.

pwm0 = &tpm_rpchip_0;

The chip ID in driver is the instance number.

rdata->chip_id = of_alias_get_id(np, "pwm");

[santhosh-madlapura]

In Addition to @niclas_karlsson  mentioned
Previously the Backlight was configured for PTA3_TPM0_CH2 (A35) which is now moved to PTC1_TPM2_CH0(M33) in our case. Does the tpm_rpchip_0 (in files "imx8ulp-rpmsg.dtsi" and "imx8ulp-rom2620-a1.dts") has to be modified?.

Kindly let us know what are the modifications in device-tree files in that case.