linux-kernel - Re: [PATCH v3 07/10] clk: clock-wizard: Update the fixed factor divisors

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Date:   Mon, 6 Jan 2020 09:47:16 +0530
From:   Shubhrajyoti Datta <shubhrajyoti.datta@...il.com>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     devel@...verdev.osuosl.org, linux-clk@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mike Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Sören Brinkmann <soren.brinkmann@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: Re: [PATCH v3 07/10] clk: clock-wizard: Update the fixed factor divisors

On Mon, Jan 6, 2020 at 1:30 AM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting shubhrajyoti.datta@...il.com (2019-11-27 22:36:14)
> > From: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
> >
> > Update the fixed factor clock registration to register the divisors.
> >
> > Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
> > ---
> >  drivers/clk/clk-xlnx-clock-wizard.c | 17 +++++++++++------
> >  1 file changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/clk/clk-xlnx-clock-wizard.c b/drivers/clk/clk-xlnx-clock-wizard.c
> > index 4c6155b..75ea745 100644
> > --- a/drivers/clk/clk-xlnx-clock-wizard.c
> > +++ b/drivers/clk/clk-xlnx-clock-wizard.c
> > @@ -491,9 +491,11 @@ static int clk_wzrd_probe(struct platform_device *pdev)
> >         u32 reg, reg_f, mult;
> >         unsigned long rate;
> >         const char *clk_name;
> > +       void __iomem *ctrl_reg;
> >         struct clk_wzrd *clk_wzrd;
> >         struct resource *mem;
> >         int outputs;
> > +       unsigned long flags = 0;
> >         struct device_node *np = pdev->dev.of_node;
> >
> >         clk_wzrd = devm_kzalloc(&pdev->dev, sizeof(*clk_wzrd), GFP_KERNEL);
> > @@ -564,19 +566,22 @@ static int clk_wzrd_probe(struct platform_device *pdev)
> >                 goto err_disable_clk;
> >         }
> >
> > -       /* register div */
> > -       reg = (readl(clk_wzrd->base + WZRD_CLK_CFG_REG(0)) &
> > -                       WZRD_DIVCLK_DIVIDE_MASK) >> WZRD_DIVCLK_DIVIDE_SHIFT;
> > +       outputs = of_property_count_strings(np, "clock-output-names");
> > +       if (outputs == 1)
> > +               flags = CLK_SET_RATE_PARENT;
>
> What does the number of clk outputs have to do with the ability to
> change the rate of a parent clk? The commit text doesn't inform me of
> what this is for either. Please help us understand.

If there are multiple clocks then changing the rate of the parent
changes the rate of all the
outputs so we donot allow changing the rate of the parent if there are
multiple clocks.
If there is only one output then that is not an issue.

I will update the description in the next version.
>
> >         clk_name = kasprintf(GFP_KERNEL, "%s_mul_div", dev_name(&pdev->dev));
> >         if (!clk_name) {
> >                 ret = -ENOMEM;
> >                 goto err_rm_int_clk;
> >         }
> >