linux-kernel - Re: [PATCH v5 4/5] ARM: dts: da850-evm: enable cpufreq

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Message-ID: <CAMpxmJW9yWcQ8497OwOhMN8wj-Cmc3-UP7Rh-yoU_uDaQkVVSw@mail.gmail.com>
Date:   Tue, 23 Apr 2019 11:15:32 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Lechner <david@...hnology.com>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 4/5] ARM: dts: da850-evm: enable cpufreq

śr., 17 kwi 2019 o 19:09 Adam Ford <aford173@...il.com> napisał(a):
>
> On Wed, Apr 17, 2019 at 10:27 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> >
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > Enable cpufreq-dt support for da850-evm. The cvdd is supplied by the
> > tps65070 pmic with configurable output voltage. By default da850-evm
> > boards support frequencies up to 375MHz so enable this operating
> > point.
>
> Have you done any testing with the LCD on any of the devices you have?
>
> I enabled the ondemand governor, and I got a bunch of splat from the
> LCD controller:
>
> tilcdc 1e13000.display: effective pixel clock rate (50000000Hz)
> differs from the calculated rate (54000000Hz)
> tilcdc 1e13000.display: tilcdc_crtc_irq(0x00000161): FIFO underflow
> tilcdc 1e13000.display: tilcdc_crtc_irq(0x00000161): FIFO underflow
> ... [ snip]
> tilcdc 1e13000.display: effective pixel clock rate (50000000Hz)
> differs from the calculated rate (54000000Hz)
> tilcdc 1e13000.display: effective pixel clock rate (50000000Hz)
> differs from the calculated rate (54000000Hz)
> tilcdc 1e13000.display: tilcdc_crtc_irq(0x00000161): FIFO underflow
>
> It appears to go on forever.  I don't necessarily want to hold it up,
> but I don't know the clocking system well enough to know where to go
> investigate it.  I can certainly live without ondemand.  Using
> userspace as the default governor is fine for me for now.
>
> adam

Hi Adam,

I did test the tilcdc on da850-lcdk. The only message I'm getting
during transitions is a single:

tilcdc <name>: tilcdc_crtc_irq(<address>): FIFO underflow

but this is fairly normal - we also get this during modeset and it
doesn't affect the display.

The problem with the pixel clock may come from the bootloader - are
you using a recent version of u-boot?

Bart

> >
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > Reviewed-by: Adam Ford <aford173@...il.com>
> > ---
> >  arch/arm/boot/dts/da850-evm.dts | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/arch/arm/boot/dts/da850-evm.dts b/arch/arm/boot/dts/da850-evm.dts
> > index f04bc3e15332..f94bb38fdad9 100644
> > --- a/arch/arm/boot/dts/da850-evm.dts
> > +++ b/arch/arm/boot/dts/da850-evm.dts
> > @@ -191,6 +191,19 @@
> >         };
> >  };
> >
> > +&cpu {
> > +       cpu-supply = <&vdcdc3_reg>;
> > +};
> > +
> > +/*
> > + * The standard da850-evm kits and SOM's are 375MHz so enable this operating
> > + * point by default. Higher frequencies must be enabled for custom boards with
> > + * other variants of the SoC.
> > + */
> > +&opp_375 {
> > +       status = "okay";
> > +};
> > +
> >  &sata {
> >         status = "okay";
> >  };
> > --
> > 2.21.0
> >