linux-kernel - Re: [PATCH v2 3/4] clk: tegra: Add quirk for getting CDEV1/2 clocks

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Date:   Tue, 8 May 2018 13:54:31 +0300
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        Marcel Ziswiler <marcel@...wiler.com>,
        Marc Dietrich <marvin24@....de>, <linux-clk@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] clk: tegra: Add quirk for getting CDEV1/2 clocks

On Fri, May 04, 2018 at 01:55:36AM +0300, Dmitry Osipenko wrote:
> CDEV1 and CDEV2 clocks are a bit special case, their parent clock is
> created by the pinctrl driver. It should be possible for clk user to
> request these clocks before pinctrl driver got probed and hence user will
> get an orphaned clock. That might be undesirable because user expects
> parent clock to be enabled by the child, so let's return EPROBE_DEFER
> until parent clock appear.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/clk/tegra/clk.c | 34 +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/tegra/clk.c b/drivers/clk/tegra/clk.c
> index ba923f0d5953..04cbe7e9eff3 100644
> --- a/drivers/clk/tegra/clk.c
> +++ b/drivers/clk/tegra/clk.c
> @@ -298,6 +298,38 @@ static struct reset_controller_dev rst_ctlr = {
>  	.of_reset_n_cells = 1,
>  };
>  
> +static struct clk *tegra_of_clk_src_onecell_get(struct of_phandle_args *clkspec,
> +						void *data)
> +{
> +	struct clk_hw *parent_hw;
> +	struct clk_hw *hw;
> +	struct clk *clk;
> +	const char *name;
> +
> +	clk = of_clk_src_onecell_get(clkspec, data);
> +	if (IS_ERR(clk))
> +		return clk;
> +
> +	name = __clk_get_name(clk);
> +
> +	/*
> +	 * Tegra20 CDEV1 and CDEV2 clocks are a bit special case, their parent
> +	 * clock is created by the pinctrl driver. It is possible for clk user
> +	 * to request these clocks before pinctrl driver got probed and hence
> +	 * user will get an orphaned clock. That might be undesirable because
> +	 * user may expect parent clock to be enabled by the child.
> +	 */
> +	if (!strcmp(name, "cdev1") || !strcmp(name, "cdev2")) {
> +		hw = __clk_get_hw(clk);
> +
> +		parent_hw = clk_hw_get_parent(hw);
> +		if (!parent_hw)
> +			return ERR_PTR(-EPROBE_DEFER);
> +	}
> +
> +	return clk;
> +}
> +

Rather than retrieving the struct clk * and comparing the names, you can use
the DT ID in  clkspec->args[0] and compare against TEGRA20_CLK_CDEV1 and
TEGRA20_CLK_CDEV2.

Peter.

>  void __init tegra_add_of_provider(struct device_node *np)
>  {
>  	int i;
> @@ -314,7 +346,7 @@ void __init tegra_add_of_provider(struct device_node *np)
>  
>  	clk_data.clks = clks;
>  	clk_data.clk_num = clk_num;
> -	of_clk_add_provider(np, of_clk_src_onecell_get, &clk_data);
> +	of_clk_add_provider(np, tegra_of_clk_src_onecell_get, &clk_data);
>  
>  	rst_ctlr.of_node = np;
>  	rst_ctlr.nr_resets = periph_banks * 32 + num_special_reset;
> -- 
> 2.17.0
>