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

On Mon, 04 Mar 2024 12:11:36 +0100 "Arnd Bergmann" arnd@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