Advice on PWM for EXTCOMIN of Sharp Memory LCD

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Advice on PWM for EXTCOMIN of Sharp Memory LCD

Sun Dec 27, 2020 4:43 am

Dear SAMA5 Linux experts,

I'm in the progress of integrating the Sharp Memory LCD (LS032B7DD02) driver into SAMA5D27-SOM1-EK based on the following patch : https://patchwork.kernel.org/project/li ... el.gov.br/.

This LCD uses SPI interface. I then re-use some of the signals of the LCD TFT interface (J26) on the SAMA5D27-SOM1-EK. Especially :
- PC3 (LCDPWM) for EXTCOMIN of LS032B7DD02,
- PC4 (LCDDISP) for DISP of LS032B7DD02,
- PA14, PA15, PA16 for SPI interface.

I do NOT have any experience with defining the PWM for the EXTCOMIN signal of the LCD in the dts. I found the AN3279 - How-to-use-SAMA5D2-PWM-Under-Linux but it is mainly about how to access / control the pwm from user-space.

I would like your advice on how to define the pwm properties in the dts of the SAMA5D27-SOM1-EK to generated the expected signal for driving the LCD.

I'm using linux4sam-6.1 kernel. Hereafter is the uncompleted display dts node in at91-sama5d27_som1_ek.dts

Code: Select all

                        spi0: spi@f8000000 {
                                pinctrl-names = "default";
                                pinctrl-0 = <&pinctrl_spi0_default>;
                                status = "okay";

                                display@0 {
                                        compatible = "sharp,ls032b7dd02";
                                        reg = <0>;
                                        spi-max-frequency = <32000000>;
                                        spi-cs-high;

                                        disp-gpios = <&gpioA PIN_PC4>;
                                        disp-active-high;
                                        sharp,extmode-high;
                                        pwms = <&hlcdc_pwm 0 50000 0>;  // I saw that hlcdc_pwm from here : https://www.acmesystems.it/roadrunner_tft, but I'm not sure if it is possible to use it and what is necessary modification in .dtsi, dts.
                                        sharp,frames-per-sec = <20>;
                                        status = "okay";
                                };
                        };

Thanks in advance and best regards,

Pascal.

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