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Date: Mon, 4 Mar 2024 12:46:01 +0100
From: Maxime Ripard <mripard@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>, 
	open list <linux-kernel@vger.kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, 
	linux-sunxi@lists.linux.dev, dri-devel@lists.freedesktop.org, lkft-triage@lists.linaro.org, 
	Dave Airlie <airlied@redhat.com>, Dan Carpenter <dan.carpenter@linaro.org>, 
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: arm: ERROR: modpost: "__aeabi_uldivmod"
 [drivers/gpu/drm/sun4i/sun4i-drm-hdmi.ko] undefined!
Message-ID: <20240304-brawny-goshawk-of-sorcery-860cef@houat>
References: <CA+G9fYvG9KE15PGNoLu+SBVyShe+u5HBLQ81+kK9Zop6u=ywmw@mail.gmail.com>
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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!
> >
>=20
> Apparently caused by the 64-bit division in 358e76fd613a
> ("drm/sun4i: hdmi: Consolidate atomic_check and mode_valid"):
>=20
>=20
> +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 =3D drm_encoder_to_sun4i_hdmi(encoder);
> -       unsigned long rate =3D mode->clock * 1000;
> -       unsigned long diff =3D rate / 200; /* +-0.5% allowed by HDMI spec=
 */
> +       const struct sun4i_hdmi *hdmi =3D drm_connector_to_sun4i_hdmi(con=
nector);
> +       unsigned long diff =3D clock / 200; /* +-0.5% allowed by HDMI spe=
c */
>         long rounded_rate;
>=20
> 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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