arm: ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!

[Andre Przywara]

On Mon, 04 Mar 2024 12:11:36 +0100
"Arnd Bergmann" <arnd at arndb.de> wrote:

Hi,

> On Mon, Mar 4, 2024, at 09:07, Naresh Kamboju wrote:
> > The arm defconfig builds failed on today's Linux next tag next-20240304.
> >
> > Build log:
> > ---------
> > ERROR: modpost: "__aeabi_uldivmod"
> > [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!
> >  
> 
> Apparently caused by the 64-bit division in 358e76fd613a
> ("drm/sun4i: hdmi: Consolidate atomic_check and mode_valid"):
> 
> 
> +static enum drm_mode_status
> +sun4i_hdmi_connector_clock_valid(const struct drm_connector *connector,
> +                                const struct drm_display_mode *mode,
> +                                unsigned long long clock)
>  {
> -       struct sun4i_hdmi *hdmi = drm_encoder_to_sun4i_hdmi(encoder);
> -       unsigned long rate = mode->clock * 1000;
> -       unsigned long diff = rate / 200; /* +-0.5% allowed by HDMI spec */
> +       const struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
> +       unsigned long diff = clock / 200; /* +-0.5% allowed by HDMI spec */

Wouldn't "div_u64(clock, 200)" solve this problem?

Cheers,
Andre

>         long rounded_rate;
> 
> This used to be a 32-bit division. If the rate is never more than
> 4.2GHz, clock could be turned back into 'unsigned long' to avoid
> the expensive div_u64().
> 
>       Arnd
>