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

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Message-ID: <20241129-mottled-satisfied-dormouse-7caf27@houat>
Date: Fri, 29 Nov 2024 15:06:45 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Nathan Chancellor <nathan@...nel.org>, 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>, 
	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 25, 2024 at 11:35:58AM +0100, Geert Uytterhoeven wrote:
> Hi Maxime,
> 
> On Fri, Nov 22, 2024 at 10:15 AM Maxime Ripard <mripard@...nel.org> wrote:
> > On Fri, Nov 22, 2024 at 09:36:16AM +0100, Geert Uytterhoeven wrote:
> > > 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?
> >
> > Do we really need that kind of comments?
> >
> > It was applied already, I made sure it's part of the next PR we send to
> > Linus. And it should be in linux-next tomorrow.
> 
> Thank you, I can confirm it is now commit 818956c76517e127
> ("drm/rockchip: avoid 64-bit division") in drm-misc/for-linux-next
> and next-20241125.
> 
> Interestingly, the commit description contains:
> 
>     (cherry picked from commit 4b64b4a81fcd51f570c046cf904aef19ec756d45)
> 
> which is not in any tree on git.kernel.org, but the github collective
> does know about it:
> https://github.com/torvalds/linux/commit/4b64b4a81fcd51f570c046cf904aef19ec756d45

The commit is in drm-misc-next, which will land in 6.14.

> Probably you want to drop that line.

We don't rebase anyway :/

Maxime

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