[PATCH v2 2/3] video: rockchip: rk3328: filter unsupported modes

[Jonas Karlman]

Hi Vasily,

On 2025-03-23 23:50, Vasily Khoruzhick wrote:
> While RK3328 is capable of 4K resolutions, dw-hdmi driver in u-boot
> seems to have some issue with 4K. 1440p or lower works fine.
> 
> Limit max resolutions to 2560x1440x60Hz, by filtering the modes with
> pixel clock > 297MHz
> 
> Fixes: f3ea872970d603 ("video: rockchip: Add rk3328 hdmi support")
> Signed-off-by: Vasily Khoruzhick <anarsoul at gmail.com>
> ---
> v2: add a comment that max pixel clock limit is a workaround
> 
> drivers/video/rockchip/rk3328_hdmi.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/video/rockchip/rk3328_hdmi.c b/drivers/video/rockchip/rk3328_hdmi.c
> index 763669c09be..ff351aaac7c 100644
> --- a/drivers/video/rockchip/rk3328_hdmi.c
> +++ b/drivers/video/rockchip/rk3328_hdmi.c
> @@ -105,9 +105,20 @@ static int rk3328_hdmi_probe(struct udevice *dev)
>  	return 0;
>  }
>  
> +static bool rk3328_hdmi_mode_valid(struct udevice *dev,
> +				   const struct display_timing *timing)
> +{
> +	/* Limit pixel clock to 297MHz. While RK3328 support higher rates and it
> +	 * works in Linux, it doesn't seem to work in u-boot. That limits max
> +	 * resolution to 1440p
> +	 */
> +	return timing->pixelclock.typ <= 297000000;

I think it make more sense to limit to the HDMI 1.4 max 340 MHz instead
of arbitrary 297 MHz. Anything above 340 MHz will require scrambling etc
and will not work in U-Boot unless at least dw-hdmi driver is updated.

Regards,
Jonas

> +}
> +
>  static const struct dm_display_ops rk3328_hdmi_ops = {
>  	.read_edid = rk_hdmi_read_edid,
>  	.enable = rk3328_hdmi_enable,
> +	.mode_valid = rk3328_hdmi_mode_valid,
>  };
>  
>  static const struct udevice_id rk3328_hdmi_ids[] = {