linux-kernel - Re: [PATCH 01/16] clk: permit to define a custom parent for clk_hw_get_parent

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Message-Id: <20220315175520.32E1AC340EE@smtp.kernel.org>
Date:   Tue, 15 Mar 2022 10:55:18 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Andy Gross <agross@...nel.org>,
        Ansuel Smith <ansuelsmth@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH 01/16] clk: permit to define a custom parent for clk_hw_get_parent_index

Quoting Ansuel Smith (2022-03-13 12:04:04)
> Clk can have multiple parents. Some clk may require to get the cached
> index of other parent that are not current associated with the clk.
> Extend clk_hw_get_parent_index() with an optional parent to permit a
> driver to get the cached index. If parent is NULL, the parent associated
> with the provided hw clk is used.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  drivers/clk/clk.c                 | 14 +++++++++-----
>  drivers/clk/tegra/clk-periph.c    |  2 +-
>  drivers/clk/tegra/clk-sdmmc-mux.c |  2 +-
>  drivers/clk/tegra/clk-super.c     |  4 ++--
>  include/linux/clk-provider.h      |  2 +-
>  5 files changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 8de6a22498e7..fe42f56bfbdf 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1711,15 +1711,19 @@ static int clk_fetch_parent_index(struct clk_core *core,
>  /**
>   * clk_hw_get_parent_index - return the index of the parent clock
>   * @hw: clk_hw associated with the clk being consumed
> + * @parent: optional clk_hw of the parent to be fetched
>   *
> - * Fetches and returns the index of parent clock. Returns -EINVAL if the given
> - * clock does not have a current parent.
> + * Fetches and returns the index of parent clock. If parent is not
> + * provided the parent of hw is used.
> + * Returns -EINVAL if the given clock does not have a current parent.
>   */
> -int clk_hw_get_parent_index(struct clk_hw *hw)
> +int clk_hw_get_parent_index(struct clk_hw *hw, struct clk_hw *parent)

Please introduce another API vs. tacking on an "output" argument to this
API. That makes the patch less invasive. And it can also return a
pointer instead of an integer in that case.

>  {
> -       struct clk_hw *parent = clk_hw_get_parent(hw);
> +       /* With parent NULL get the current parent of hw */
> +       if (!parent)
> +               parent = clk_hw_get_parent(hw);