linux-kernel - Re: [linux-sunxi] [PATCH v4 1/6] clk: sunxi-ng: div: Add support for fixed post-divider

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Date:   Mon, 26 Jun 2017 08:05:16 +1000
From:   Jonathan Liu <net147@...il.com>
To:     Priit Laes <plaes@...es.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Russell King <linux@...linux.org.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-clk@...r.kernel.org, devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH v4 1/6] clk: sunxi-ng: div: Add support for
 fixed post-divider

Hi Priit,

This is showing from clock rate of 171428572 in the output of "cat
/sys/kernel/debug/clk/clk_summary" for pll-periph-sata.
The clock rate should be 100000000 (100 MHz) when read from the hardware.

On 26 June 2017 at 06:45, Priit Laes <plaes@...es.org> wrote:
> SATA clock on sun4i/sun7i is of type (parent) / M / 6 where
> 6 is fixed post-divider.
>
> Signed-off-by: Priit Laes <plaes@...es.org>
> ---
>  drivers/clk/sunxi-ng/ccu_div.c | 12 ++++++++++--
>  drivers/clk/sunxi-ng/ccu_div.h |  3 ++-
>  2 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/sunxi-ng/ccu_div.c b/drivers/clk/sunxi-ng/ccu_div.c
> index c0e5c10..de30e15 100644
> --- a/drivers/clk/sunxi-ng/ccu_div.c
> +++ b/drivers/clk/sunxi-ng/ccu_div.c

Missing handling of fixed_post_div in ccu_div_round_rate.
ccu_div_round_rate should multiply the rate by the postdiv before
looking up the divider using divider_get_val and divide val by postdiv
just before returning.

> @@ -62,8 +62,13 @@ static unsigned long ccu_div_recalc_rate(struct clk_hw *hw,
>         parent_rate = ccu_mux_helper_apply_prediv(&cd->common, &cd->mux, -1,
>                                                   parent_rate);
>
> -       return divider_recalc_rate(hw, parent_rate, val, cd->div.table,
> -                                  cd->div.flags);
> +       val = divider_recalc_rate(hw, parent_rate, val, cd->div.table,
> +                                 cd->div.flags);
> +
> +       if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
> +               val /= cd->fixed_post_div;
> +
> +       return val;
>  }
>
>  static int ccu_div_determine_rate(struct clk_hw *hw,

> @@ -89,6 +94,9 @@ static int ccu_div_set_rate(struct clk_hw *hw, unsigned long rate,
>         val = divider_get_val(rate, parent_rate, cd->div.table, cd->div.width,
>                               cd->div.flags);
>
> +       if (cd->common.features & CCU_FEATURE_FIXED_POSTDIV)
> +               val *= cd->fixed_post_div;
> +
>         spin_lock_irqsave(cd->common.lock, flags);
>
>         reg = readl(cd->common.base + cd->common.reg);

val here is the divider value that is stored in the clock register
field not the actual rate so this is incorrect. Instead the rate needs
to be multiplied by postdiv just before divider_get_val.

> diff --git a/drivers/clk/sunxi-ng/ccu_div.h b/drivers/clk/sunxi-ng/ccu_div.h
> index 08d0744..f3a5028 100644
> --- a/drivers/clk/sunxi-ng/ccu_div.h
> +++ b/drivers/clk/sunxi-ng/ccu_div.h
> @@ -86,9 +86,10 @@ struct ccu_div_internal {
>  struct ccu_div {
>         u32                     enable;
>
> -       struct ccu_div_internal         div;
> +       struct ccu_div_internal div;
>         struct ccu_mux_internal mux;
>         struct ccu_common       common;
> +       unsigned int            fixed_post_div;
>  };
>
>  #define SUNXI_CCU_DIV_TABLE_WITH_GATE(_struct, _name, _parent, _reg,   \
> --
> git-series 0.9.1

Thanks.

Regards,
Jonathan