linux-kernel - Re: [RESEND/PATCH v6 3/3] clk: qcom: Add A53 clock driver

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Message-ID: <20161102205910.GQ25787@tuxbot>
Date:   Wed, 2 Nov 2016 13:59:11 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>, mturquette@...libre.com,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [RESEND/PATCH v6 3/3] clk: qcom: Add A53 clock driver

On Thu 27 Oct 18:54 PDT 2016, Stephen Boyd wrote:

> On 10/19, Georgi Djakov wrote:
> > Add a driver for the A53 Clock Controller. It is a hardware block that
> > implements a combined mux and half integer divider functionality. It can
> > choose between a fixed-rate clock or the dedicated A53 PLL. The source
> > and the divider can be set both at the same time.
> > 
> > This is required for enabling CPU frequency scaling on platforms like
> > MSM8916.
> > 
> 
> Please Cc DT reviewers.
> 
> > Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
> > ---
> >  .../devicetree/bindings/clock/qcom,a53cc.txt       |  22 +++
> >  drivers/clk/qcom/Kconfig                           |   8 ++
> >  drivers/clk/qcom/Makefile                          |   1 +
> >  drivers/clk/qcom/a53cc.c                           | 155 +++++++++++++++++++++
> >  4 files changed, 186 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/clock/qcom,a53cc.txt
> >  create mode 100644 drivers/clk/qcom/a53cc.c
> > 
> > diff --git a/Documentation/devicetree/bindings/clock/qcom,a53cc.txt b/Documentation/devicetree/bindings/clock/qcom,a53cc.txt
> > new file mode 100644
> > index 000000000000..a025f062f177
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/qcom,a53cc.txt
> > @@ -0,0 +1,22 @@
> > +Qualcomm A53 CPU Clock Controller Binding
> > +------------------------------------------------
> > +The A53 CPU Clock Controller is hardware, which provides a combined
> > +mux and divider functionality for the CPU clocks. It can choose between
> > +a fixed rate clock and the dedicated A53 PLL.
> > +
> > +Required properties :
> > +- compatible : shall contain:
> > +
> > +			"qcom,a53cc"
> > +
> > +- reg : shall contain base register location and length
> > +	of the APCS region
> > +- #clock-cells : shall contain 1
> > +
> > +Example:
> > +
> > +	apcs: syscon@...1000 {
> > +		compatible = "qcom,a53cc", "syscon";
> 
> Why is it a syscon? Is that part used?
> 

I use the register at offset 8 for interrupting the other subsystems, so
this must be available as something I can poke.

Which makes me think that this should be described as a "simple-mfd" and
"syscon" with the a53cc node as a child - grabbing the regmap of the
syscon parent, rather then ioremapping the same region again.

Regards,
Bjorn