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

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Date: Mon, 04 Mar 2024 12:11:36 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Naresh Kamboju" <naresh.kamboju@...aro.org>,
 "open list" <linux-kernel@...r.kernel.org>,
 "Linux ARM" <linux-arm-kernel@...ts.infradead.org>,
 linux-sunxi@...ts.linux.dev, dri-devel@...ts.freedesktop.org,
 lkft-triage@...ts.linaro.org
Cc: "Maxime Ripard" <mripard@...nel.org>, "Dave Airlie" <airlied@...hat.com>,
 "Dan Carpenter" <dan.carpenter@...aro.org>,
 "Ard Biesheuvel" <ardb@...nel.org>
Subject: Re: arm: ERROR: modpost: "__aeabi_uldivmod"
 [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!

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 */
        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