Re: [PATCH v2 5/5] arm64: dts: renesas: Add LCDC overlays for RZ/T2H and RZ/N2H EVKs with ADV7513

[Geert Uytterhoeven]

Hi Prabhakar,

On Mon, 15 Jun 2026 at 13:55, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> Add DT overlay support enabling the DU/LCDC pipeline on the RZ/T2H
> (r9a09g077) and RZ/N2H (r9a09g087) evaluation kits when fitted with a
> CN15/CN20 ADV7513 HDMI transmitter.
>
> Move the LED8 and LED9 preprocessor conditionals inside the node
> definitions so that the nodes remain present in the base DTS. This
> allows the LCDC overlay to reference and disable them when their pins
> are reassigned to display functions.
>
> According to the hardware manual, the LCDC pins should use slew-rate
> setting 1 (fast). However, testing on the RZ/T2H and RZ/N2H EVKs with
> the ADV7513 HDMI transmitter showed unstable display output with visible
> screen flicker when configured for fast slew-rate operation. Configure
> the LCDC pins with slew-rate setting 0 (slow) instead, which provides
> stable display output on the evaluation platforms.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Thanks for your patch!

> --- /dev/null
> +++ b/arch/arm64/boot/dts/renesas/r9a09g077m44-evk-cn15-lcdc.dtso

> +/*
> + * RZ/T2H LCDC configuration:
> + * ----------------------------------------------------------
> + * Function        Pin     SW Setting
> + * ----------------------------------------------------------
> + * LCDC_DATG0     P11_0, SW6[3]: OFF, SW6[4]: ON, SW6[5]: OFF
> + * LCDC_DATB1     P18_0, SW8[3]: OFF, SW8[4]: ON
> + * LCDC_DATB2     P18_1, SW8[1]: OFF, SW8[2]: ON
> + * HEADER_IRQ8    P22_6, SW2[1]: ON, SW2[2]: OFF

What is IRQ8 connected to on the display board?
It is not described in the .dts[io].

BTW, r9a09g077m44-rzt2h-evk.dts uses a mix of "SWx[y]" and "SWx-y" (and
tables), which makes it harder than needed to see which functionality
is affected by a given switch.

> + */
> +#include "rzt2h-n2h-evk-du-adv7513.dtsi"

In case of dynamic overlays, any conflicting pins must be disabled
first, so please move this #include to the end of this file.

> +
> +&{/leds/led-4} {
> +       /* P18_0 is used for DU function LCDC_DATB1. */
> +       status = "disabled";
> +};
> +
> +&{/leds/led-5} {
> +       /* P18_1 is used for DU function LCDC_DATB2. */
> +       status = "disabled";
> +};
> +
> +/*
> + * Disable SDHI0 as SW2 settings for eMMC/SD card conflict with DU pin
> + * settings.
> + */
> +&sdhi0 {
> +       status = "disabled";
> +};

> --- /dev/null
> +++ b/arch/arm64/boot/dts/renesas/r9a09g087m44-evk-cn20-lcdc.dtso

> +/*
> + * RZ/N2H LCDC configuration:
> + * ----------------------------------------------------------
> + * Function        Pin     SW Setting
> + * ----------------------------------------------------------
> + * LCDC_DATG0     P11_0, DSW12[3]: ON, DSW12[4]: OFF
> + * LCDC_DATG3     P14_3, DSW18[5]: OFF, DSW18[6]: ON

and DSW19[3]: OFF, DSW19[4]: ON?

> + * LCDC_DATG6     P14_6, DSW15[8]: ON, DSW15[9]: OFF, DSW15[10]: OFF
> + * LCDC_DATB2     P18_1, DSW18[9]: OFF, DSW18[10]: ON
> + * I2C_SDA1       P03_3, DSW7[1]: ON, DSW7[2]: OFF
> + * I2C_SCL1       P03_4, DSW7[3]: ON, DSW7[4]: OFF

I2C_SDA1 and I2C_SCL1 are exchanged?

BTW, r9a09g087m44-rzn2h-evk.dts uses a mix of "SWx[y]" and "SWx-y" (and
tables), which makes it harder than needed to see which functionality
is affected by a given switch.

> + * ------------------------------------------------
> + */
> +
> +#include "rzt2h-n2h-evk-du-adv7513.dtsi"

In case of dynamic overlays, any conflicting pins must be disabled
first, so please move this #include to the end of this file.

> +
> +&{/keys/key-1} {
> +       /* P18_2 is used for DU function LCDC_DATB3. */
> +       status = "disabled";
> +};
> +
> +&{/leds/led-4} {
> +       /* P18_1 is used for DU function LCDC_DATB2. */
> +       status = "disabled";
> +};
> +
> +&{/leds/led-7} {
> +       /* P14_3 is used for DU function LCDC_DATG3. */
> +       status = "disabled";
> +};
> +
> +&{/leds/led-8} {
> +       /* P14_6 is used for DU function LCDC_DATG6. */
> +       status = "disabled";
> +};
> +
> +&i2c0 {
> +       status = "disabled";

Needs the same comment as led-8 above?

The rest LGTM.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds