linux-kernel - Re: [PATCH] drm/rockchip: avoid 64-bit division

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Message-ID: <CAMuHMdXrrCiLm2sQmpegtVHV8X5AUp-8E5BejDxRpMbeAfHhvQ@mail.gmail.com>
Date: Fri, 22 Nov 2024 09:36:16 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...nel.org>, Sandy Huang <hjc@...k-chips.com>, 
	Heiko Stübner <heiko@...ech.de>, 
	Andy Yan <andy.yan@...k-chips.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Algea Cao <algea.cao@...k-chips.com>, 
	Cristian Ciocaltea <cristian.ciocaltea@...labora.com>, Arnd Bergmann <arnd@...db.de>, 
	dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/rockchip: avoid 64-bit division

On Mon, Nov 4, 2024 at 6:30 PM Nathan Chancellor <nathan@...nel.org> wrote:
> On Fri, Oct 18, 2024 at 03:10:10PM +0000, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > Dividing a 64-bit integer prevents building this for 32-bit targets:
> >
> > ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/rockchip/rockchipdrm.ko] undefined!
> >
> > As this function is not performance criticial, just Use the div_u64() helper.
> >
> > Fixes: 128a9bf8ace2 ("drm/rockchip: Add basic RK3588 HDMI output support")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
>
> Can someone please pick this up? It is still broken in next-20241104...
>
> https://storage.tuxsuite.com/public/clangbuiltlinux/continuous-integration2/builds/2oNvJFRj8tkDieb6VfrMf4rh1Kn/build.log
>
> > ---
> >  drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
> > index 9c796ee4c303..c8b362cc2b95 100644
> > --- a/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
> > +++ b/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
> > @@ -82,7 +82,7 @@ static void dw_hdmi_qp_rockchip_encoder_enable(struct drm_encoder *encoder)
> >                * comment in rk_hdptx_phy_power_on() from
> >                * drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> >                */
> > -             phy_set_bus_width(hdmi->phy, rate / 100);
> > +             phy_set_bus_width(hdmi->phy, div_u64(rate, 100));
> >       }
> >  }

noreply@...erman.id.au has just told me this build issue is now upstream:

    FAILED linus/m68k-allmodconfig/m68k-gcc8.1 Fri Nov 22, 05:34
    http://kisskb.ellerman.id.au/kisskb/buildresult/15277242/

    Commit:   Merge tag 'drm-next-2024-11-21' of
https://gitlab.freedesktop.org/drm/kernel
              28eb75e178d389d325f1666e422bc13bbbb9804c
    Compiler: m68k-linux-gcc (GCC) 8.1.0 / GNU ld (GNU Binutils) 2.30

    ERROR: modpost: "__udivdi3"
[drivers/gpu/drm/rockchip/rockchipdrm.ko] undefined!

Applying this patch fixes it, so
Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Do we really need +5 weeks to apply a fix for a reported build issue?
Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds