linux-kernel - Re: [PATCH v4 4/7] drm/vc4: hdmi: Fix hdmi_enable

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Message-ID: <CAPY8ntB1bgHVFMAYP62oGXPUwL4YkGMkxWJaoHLeNW=G1rj+Hw@mail.gmail.com>
Date:   Wed, 26 Oct 2022 16:36:04 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     maxime@...no.tech
Cc:     Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Ray Jui <rjui@...adcom.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Stefan Wahren <stefan.wahren@...e.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Dom Cobley <popcornmix@...il.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 4/7] drm/vc4: hdmi: Fix hdmi_enable_4kp60 detection

On Wed, 26 Oct 2022 at 16:27, Dave Stevenson
<dave.stevenson@...pberrypi.com> wrote:
>
> On Thu, 20 Oct 2022 at 10:14, <maxime@...no.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 the
> > maximum rate allowed on that clock and fix the 4k@...z output.
> >
> > Fixes: e9d6cea2af1c ("clk: bcm: rpi: Run some clocks at the minimum rate allowed")
> > Signed-off-by: Maxime Ripard <maxime@...no.tech>
>
> Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.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, struct device *master, void *data)
> >
> >         if (variant->max_pixel_clock == 600000000) {
> >                 struct vc4_dev *vc4 = to_vc4_dev(drm);
> > -               long max_rate = clk_round_rate(vc4->hvs->core_clk, 550000000);
> > +               unsigned long max_rate = rpi_firmware_clk_get_max_rate(vc4->hvs->core_clk);

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.

clk_round_rate returned a long, and therefore previously it did have to be that.

  Dave

> >                 if (max_rate < 550000000)
> >                         vc4_hdmi->disable_4kp60 = true;
> >
> > --
> > b4 0.10.1