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From:   maxime@cerno.tech
Date:   Wed, 26 Oct 2022 18:10:48 +0200
To:     Dave Stevenson <dave.stevenson@raspberrypi.com>
Cc:     Daniel Vetter <daniel@ffwll.ch>, Emma Anholt <emma@anholt.net>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, Ray Jui <rjui@broadcom.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Dom Cobley <popcornmix@gmail.com>, linux-clk@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org
Subject: Re: [PATCH v4 4/7] drm/vc4: hdmi: Fix hdmi_enable_4kp60 detection
Message-ID: <20221026161048.qsiurbhlova4ndud@houat>
References: <20220815-rpi-fix-4k-60-v4-0-a1b40526df3e@cerno.tech>
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 <CAPY8ntAkzWOy0fk4ojtKW9k7asH1zOYygoU8B_=yJjm7Ni7isw@mail.gmail.com>
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Hi Dave,

Thanks for your review

On Wed, Oct 26, 2022 at 04:36:04PM +0100, Dave Stevenson wrote:
> On Wed, 26 Oct 2022 at 16:27, Dave Stevenson
> <dave.stevenson@raspberrypi.com> wrote:
> >
> > On Thu, 20 Oct 2022 at 10:14, <maxime@cerno.tech> wrote:
> > >
> > > In order to support higher HDMI frequencies, users have to set the
> > > hdmi_enable_4kp60 parameter in their config.txt file.
> > >
> > > We were detecting this so far by calling clk_round_rate() on the core
> > > clock with the frequency we're supposed to run at when one of those
> > > modes is enabled. Whether or not the parameter was enabled could then=
 be
> > > inferred by the returned rate since the maximum clock rate reported by
> > > the firmware was one of the side effect of setting that parameter.
> > >
> > > However, the recent clock rework we did changed what clk_round_rate()
> > > was returning to always return the minimum allowed, and thus this test
> > > wasn't reliable anymore.
> > >
> > > Let's use the new clk_get_max_rate() function to reliably determine t=
he
> > > maximum rate allowed on that clock and fix the 4k@60Hz output.
> > >
> > > Fixes: e9d6cea2af1c ("clk: bcm: rpi: Run some clocks at the minimum r=
ate allowed")
> > > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> >
> > Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> >
> > > ---
> > >  drivers/gpu/drm/vc4/vc4_hdmi.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4=
_hdmi.c
> > > index 64f9feabf43e..87961d4de5aa 100644
> > > --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> > > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> > > @@ -46,6 +46,7 @@
> > >  #include <linux/pm_runtime.h>
> > >  #include <linux/rational.h>
> > >  #include <linux/reset.h>
> > > +#include <soc/bcm2835/raspberrypi-clocks.h>
> > >  #include <sound/dmaengine_pcm.h>
> > >  #include <sound/hdmi-codec.h>
> > >  #include <sound/pcm_drm_eld.h>
> > > @@ -3429,7 +3430,7 @@ static int vc4_hdmi_bind(struct device *dev, st=
ruct device *master, void *data)
> > >
> > >         if (variant->max_pixel_clock =3D=3D 600000000) {
> > >                 struct vc4_dev *vc4 =3D to_vc4_dev(drm);
> > > -               long max_rate =3D clk_round_rate(vc4->hvs->core_clk, =
550000000);
> > > +               unsigned long max_rate =3D rpi_firmware_clk_get_max_r=
ate(vc4->hvs->core_clk);
>=20
> Actually minor nit:
> rpi_firmware_clk_get_max_rate returns an unsigned int.
> AFAICT we don't need the range of unsigned long in any subsequent
> code, so I think it could just be unsigned int here.
>=20
> clk_round_rate returned a long, and therefore previously it did have to b=
e that.

Yeah, I was actually two-minded about this.
rpi_firmware_clk_get_max_rate() indeed returns an unsigned long, because
that's what the firmware returns.

But the clock framework uses unsigned long to store all its frequencies,
and in our case here in clk_set_min_rate().

I don't mind changing it to unsigned int here if you prefer to, and if
you're fine with the rest of the patches I can fix it up while applying
the patches.

Maxime