From: Rob Herring <robh+dt@kernel.org>
To: Anson Huang <anson.huang@nxp.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"Angus Ainslie (Purism)" <angus@akkea.ca>,
"Jacky Bai" <ping.bai@nxp.com>,
"Carlo Caione" <ccaione@baylibre.com>,
"Andrey Smirnov" <andrew.smirnov@gmail.com>,
"Fabio Estevam" <festevam@gmail.com>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Daniel Lezcano" <daniel.lezcano@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Daniel Baluta" <daniel.baluta@nxp.com>,
"Abel Vesa" <abel.vesa@nxp.com>, dl-linux-imx <linux-imx@nxp.com>,
"Sascha Hauer" <kernel@pengutronix.de>,
"Viresh Kumar" <viresh.kumar@linaro.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Leonard Crestez" <leonard.crestez@nxp.com>,
"Shawn Guo" <shawnguo@kernel.org>,
"Guido Günther" <agx@sigxcpu.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
"Lucas Stach" <l.stach@pengutronix.de>
Subject: Re: [PATCH V4 2/5] clocksource/drivers/sysctr: Add clock-frequency property
Date: Wed, 10 Jul 2019 07:23:23 -0600 [thread overview]
Message-ID: <CAL_JsqJbHFZ2qcLvhZGk8Q-f80_QhdgQxcHe2TyCjc4GGRNJNQ@mail.gmail.com> (raw)
In-Reply-To: <DB3PR0402MB39167FC68991F071E9E58D81F5F00@DB3PR0402MB3916.eurprd04.prod.outlook.com>
On Tue, Jul 9, 2019 at 7:30 PM Anson Huang <anson.huang@nxp.com> wrote:
>
> Hi, Rob
>
> > On Mon, Jul 1, 2019 at 3:47 AM <Anson.Huang@nxp.com> wrote:
> > >
> > > From: Anson Huang <Anson.Huang@nxp.com>
> >
> > 'dt-bindings: timer: ...' for the subject.
>
> OK, I made a mistake.
>
> >
> > >
> > > Systems which use platform driver model for clock driver require the
> > > clock frequency to be supplied via device tree when system counter
> > > driver is enabled.
> >
> > This is a DT binding. What's a platform driver?
>
> It is just trying to explain why we need to introduce this "clock-frequency"
> property, nothing about the binding and platform driver.
>
> >
> > >
> > > This is necessary as in the platform driver model the of_clk
> > > operations do not work correctly because system counter driver is
> > > initialized in early phase of system boot up, and clock driver using
> > > platform driver model is NOT ready at that time, it will cause system
> > > counter driver initialization failed.
> > >
> > > Add clock-frequency property to the device tree bindings of the NXP
> > > system counter, so the driver can tell timer-of driver to get clock
> > > frequency from DT directly instead of doing of_clk operations via clk
> > > APIs.
> >
> > While you've now given a good explanation why you need this, it all sounds
> > like linux specific issues and a DT change should not be necessary.
> >
> > Presumably, 'clocks' points to a fixed-clock node, right? Just parse the 'clocks'
> > phandle and fetch the frequency from that node if you need to get the
> > frequency 'early'.
>
> Sound like a better solution, I will try that, since the system counter's clock is
> from osc_24m and divided by 3, since different platforms may have different divider,
> so maybe I can create a fixed-clock node in DT, then system counter driver can parse
> the clock and fetch the frequency from that node, will redo a V5 patch.
The divide by 3 can be implied by the compatible. If you need a
different divider, add another compatible.
> >
> > > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> > > ---
> > > No change.
> > > ---
> > > .../devicetree/bindings/timer/nxp,sysctr-timer.txt | 15 +++++++++------
> > > 1 file changed, 9 insertions(+), 6 deletions(-)
> > >
> > > diff --git
> > > a/Documentation/devicetree/bindings/timer/nxp,sysctr-timer.txt
> > > b/Documentation/devicetree/bindings/timer/nxp,sysctr-timer.txt
> > > index d576599..7088a0e 100644
> > > --- a/Documentation/devicetree/bindings/timer/nxp,sysctr-timer.txt
> > > +++ b/Documentation/devicetree/bindings/timer/nxp,sysctr-timer.txt
> > > @@ -11,15 +11,18 @@ Required properties:
> > > - reg : Specifies the base physical address and size of the comapre
> > > frame and the counter control, read & compare.
> > > - interrupts : should be the first compare frames' interrupt
> > > -- clocks : Specifies the counter clock.
> > > -- clock-names: Specifies the clock's name of this module
> > > +- clocks : Specifies the counter clock, mutually exclusive with clock-
> > frequency.
> > > +- clock-names : Specifies the clock's name of this module, mutually
> > exclusive with
> > > + clock-frequency.
> > > +- clock-frequency : Specifies system counter clock frequency, mutually
> > exclusive with
> > > + clocks/clock-names.
> >
> > It doesn't really work to say one or the other is needed unless you make the
> > OS support both cases.
>
> The OS already support both cases now with this patch series.
What about FreeBSD or any other OS?
Rob
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next prev parent reply other threads:[~2019-07-10 13:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 9:38 [PATCH V4 1/5] clocksource: timer-of: Support getting clock frequency from DT Anson.Huang
2019-07-01 9:38 ` [PATCH V4 2/5] clocksource/drivers/sysctr: Add clock-frequency property Anson.Huang
2019-07-09 20:30 ` Rob Herring
2019-07-10 1:30 ` Anson Huang
2019-07-10 13:23 ` Rob Herring [this message]
2019-07-11 1:04 ` Anson Huang
2019-07-01 9:38 ` [PATCH V4 3/5] clocksource: imx-sysctr: Make timer work with clock driver using platform driver model Anson.Huang
2019-07-01 9:38 ` [PATCH V4 4/5] arm64: dts: imx8mq: Add system counter node Anson.Huang
2019-07-01 9:38 ` [PATCH V4 5/5] arm64: dts: imx8mm: " Anson.Huang
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