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

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Message-ID: <20240304-brawny-goshawk-of-sorcery-860cef@houat>
Date: Mon, 4 Mar 2024 12:46:01 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: 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, 
	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!

Hi,

On Mon, Mar 04, 2024 at 12:11:36PM +0100, Arnd Bergmann wrote:
> 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().

I sent a fix for it this morning:
https://lore.kernel.org/r/20240304091225.366325-1-mripard@kernel.org

The framework will pass an unsigned long long because HDMI character
rates can go up to 5.9GHz.

Maxime

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