linux-kernel - Re: [PATCH v6 2/5] clk: meson: add support for A1 PLL clock ops

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Date:   Sat, 18 Jan 2020 22:57:01 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Jian Hu <jian.hu@...ogic.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Rob Herring <robh@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Qiufang Dai <qiufang.dai@...ogic.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        Chandle Zou <chandle.zou@...ogic.com>,
        linux-clk@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 2/5] clk: meson: add support for A1 PLL clock ops

Hi Jian,

thank you for the update!

On Thu, Jan 16, 2020 at 9:04 AM Jian Hu <jian.hu@...ogic.com> wrote:
>
> Compared with the previous SoCs, self-adaption current module
> is newly added for A1, and there is no reset parm except the
> fixed pll. In A1 PLL, the PLL enable sequence is different, using
> the new power-on sequence to enable the PLL.
>
> Signed-off-by: Jian Hu <jian.hu@...ogic.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>

[...]
> @@ -323,13 +330,34 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
>                 return 0;
>
>         /* Make sure the pll is in reset */
> -       meson_parm_write(clk->map, &pll->rst, 1);
> +       if (MESON_PARM_APPLICABLE(&pll->rst))
> +               meson_parm_write(clk->map, &pll->rst, 1);
>
>         /* Enable the pll */
>         meson_parm_write(clk->map, &pll->en, 1);
>
>         /* Take the pll out reset */
> -       meson_parm_write(clk->map, &pll->rst, 0);
> +       if (MESON_PARM_APPLICABLE(&pll->rst))
> +               meson_parm_write(clk->map, &pll->rst, 0);
> +
> +       /*
> +        * Compared with the previous SoCs, self-adaption current module
> +        * is newly added for A1, keep the new power-on sequence to enable the
> +        * PLL. The sequence is:
> +        * 1. enable the pll, delay for 10us
> +        * 2. enable the pll self-adaption current module, delay for 40us
> +        * 3. enable the lock detect module
> +        */
> +       if (MESON_PARM_APPLICABLE(&pll->current_en)) {
> +               udelay(10);
> +               meson_parm_write(clk->map, &pll->current_en, 1);
> +               udelay(40);
note to myself: first I thought that these have to be converted to ulseep_range
BUT: clk_enable can be called from atomic context, so the atomic
versions (udelay instead of usleep/usleep_range) are perfectly fine in
Jian's patch


Martin