From: Linus Walleij <linus.walleij@linaro.org>
To: Brian Masney <masneyb@onstation.org>
Cc: Taniya Das <tdas@codeaurora.org>, Stephen Boyd <sboyd@kernel.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Michael Turquette <mturquette@baylibre.com>,
Linux Input <linux-input@vger.kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
MSM <linux-arm-msm@vger.kernel.org>,
linux-clk <linux-clk@vger.kernel.org>
Subject: Re: [PATCH 1/7] clk: qcom: add support for setting the duty cycle
Date: Fri, 13 Dec 2019 14:56:30 +0100 [thread overview]
Message-ID: <CACRpkdY+yP6-MyFw1tFvVN_FjNfPBGYZxiK5rZiS5Yyp7eainw@mail.gmail.com> (raw)
In-Reply-To: <20191210115153.GA10298@onstation.org>
On Tue, Dec 10, 2019 at 12:52 PM Brian Masney <masneyb@onstation.org> wrote:
> On Tue, Dec 10, 2019 at 04:47:35AM +0000, Taniya Das wrote:
> > On 12/5/2019 5:54 AM, Brian Masney wrote:
> > > I'm not sure about the relationship of the m, n, and d values,
> > > especially how the 50% duty cycle is calculated by inverting the n
> > > value, so that's why I'm saving the duty cycle ratio for
> > > get_duty_cycle().
(...)
> > > +static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
> > > +{
> > > + struct clk_rcg2 *rcg = to_clk_rcg2(hw);
> > > + int ret, d_reg_val, mask;
> > > +
> > > + mask = BIT(rcg->mnd_width - 1) - 1;
> > > + d_reg_val = mask - (((mask - 17) * duty->num) / duty->den);
> > > + ret = __clk_rcg2_configure_with_duty_cycle(rcg, rcg->freq_tbl,
> > > + d_reg_val, duty->num,
> > > + duty->den);
> >
> > The duty-cycle calculation is not accurate.
> > There is already a plan to submit the duty-cycle changes from my side.
>
> OK... I assume that the m and n values need to be changed as well. I
> couldn't find any docs online about the meaning of the m, n, and d
> values and how they relate to each other.
I have also at times struggled to understand this.
If someone could just in a very concise form describe how these
rcg[2] clock dividers work and how m,n,d work that'd be GREAT.
ASCII art etc would be a bonus :)
Like with a patch with a big comment in
drivers/clk/qcom/clk-rcg.h
As these tend to be quite regularly reused and incarnated in
ever new silicon a complete picture for developers would be
much appreciated.
Yours,
Linus Walleij
next prev parent reply other threads:[~2019-12-13 20:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 0:24 [PATCH 0/7] qcom: add clk-vibrator driver Brian Masney
2019-12-05 0:24 ` [PATCH 1/7] clk: qcom: add support for setting the duty cycle Brian Masney
2019-12-10 4:47 ` Taniya Das
2020-02-12 23:23 ` Stephen Boyd
[not found] ` <0101016eee224b50-8a5545e2-837f-41c2-9574-b385e111a6b3-000000@us-west-2.amazonses.com>
2019-12-10 11:51 ` Brian Masney
2019-12-13 13:56 ` Linus Walleij [this message]
2019-12-05 0:24 ` [PATCH 2/7] dt-bindings: Input: drop msm-vibrator in favor of clk-vibrator Brian Masney
2019-12-17 14:11 ` Rob Herring
2019-12-05 0:24 ` [PATCH 3/7] Input: drop msm-vibrator in favor of clk-vibrator driver Brian Masney
2020-02-11 12:18 ` Brian Masney
2019-12-05 0:25 ` [PATCH 4/7] dt-bindings: Input: introduce new clock vibrator bindings Brian Masney
2019-12-05 13:56 ` Rob Herring
2019-12-09 0:54 ` Brian Masney
2019-12-09 16:16 ` Rob Herring
2019-12-09 16:55 ` Brian Masney
2020-01-05 8:35 ` Stephen Boyd
2020-01-07 12:03 ` Brian Masney
2020-01-07 17:52 ` Stephen Boyd
2020-01-07 23:18 ` Brian Masney
2019-12-05 0:25 ` [PATCH 5/7] Input: introduce new clock vibrator driver Brian Masney
2019-12-05 0:25 ` [PATCH 6/7] ARM: qcom_defconfig: drop msm-vibrator in favor of clk-vibrator driver Brian Masney
2019-12-05 0:25 ` [PATCH 7/7] ARM: dts: qcom: msm8974-hammerhead: add support for vibrator Brian Masney
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