linux-kernel - Re: [PATCH] clk: Use parent node pointer during registration if necessary

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Message-ID: <20200103001710.indj23ajryzj77bf@flawful.org>
Date:   Fri, 3 Jan 2020 01:17:10 +0100
From:   Niklas Cassel <nks@...wful.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Niklas Cassel <niklas.cassel@...aro.org>
Subject: Re: [PATCH] clk: Use parent node pointer during registration if
 necessary

On Mon, Dec 30, 2019 at 11:04:55AM -0800, Stephen Boyd wrote:
> Sometimes clk drivers are attached to devices which are children of a
> parent device that is connected to a node in DT. This happens when
> devices are MFD-ish and the parent device driver mostly registers child
> devices to match against drivers placed in their respective subsystem
> directories like drivers/clk, drivers/regulator, etc. When the clk
> driver calls clk_register() with a device pointer, that struct device
> pointer won't have a device_node associated with it because it was
> created purely in software as a way to partition logic to a subsystem.
> 
> This causes problems for the way we find parent clks for the clks
> registered by these child devices because we look at the registering
> device's device_node pointer to lookup 'clocks' and 'clock-names'
> properties. Let's use the parent device's device_node pointer if the
> registering device doesn't have a device_node but the parent does. This
> simplifies clk registration code by avoiding the need to assign some
> device_node to the device registering the clk.
> 
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Reported-by: Niklas Cassel <niklas.cassel@...aro.org>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> ---
> 
> I decided to introduce a new function instead of trying to jam it all
> in the one line where we assign np. This way the function gets the 
> true 'np' as an argument all the time.
> 
>  drivers/clk/clk.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> 
> base-commit: e42617b825f8073569da76dc4510bfa019b1c35a
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index b68e200829f2..a743fffe8e46 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3719,6 +3719,28 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
>  	return ERR_PTR(ret);
>  }
>  
> +/**
> + * dev_or_parent_of_node - Get device node of @dev or @dev's parent
> + * @dev: Device to get device node of
> + *
> + * Returns: device node pointer of @dev, or the device node pointer of
> + * @dev->parent if dev doesn't have a device node, or NULL if neither
> + * @dev or @dev->parent have a device node.
> + */
> +static struct device_node *dev_or_parent_of_node(struct device *dev)
> +{
> +	struct device_node *np;
> +
> +	if (!dev)
> +		return NULL;
> +
> +	np = dev_of_node(dev);
> +	if (!np)
> +		np = dev_of_node(dev->parent);
> +
> +	return np;
> +}
> +
>  /**
>   * clk_register - allocate a new clock, register it and return an opaque cookie
>   * @dev: device that is registering this clock
> @@ -3734,7 +3756,7 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
>   */
>  struct clk *clk_register(struct device *dev, struct clk_hw *hw)
>  {
> -	return __clk_register(dev, dev_of_node(dev), hw);
> +	return __clk_register(dev, dev_or_parent_of_node(dev), hw);
>  }
>  EXPORT_SYMBOL_GPL(clk_register);
>  
> @@ -3750,7 +3772,8 @@ EXPORT_SYMBOL_GPL(clk_register);
>   */
>  int clk_hw_register(struct device *dev, struct clk_hw *hw)
>  {
> -	return PTR_ERR_OR_ZERO(__clk_register(dev, dev_of_node(dev), hw));
> +	return PTR_ERR_OR_ZERO(__clk_register(dev, dev_or_parent_of_node(dev),
> +			       hw));
>  }
>  EXPORT_SYMBOL_GPL(clk_hw_register);
>  

Reviewed-by: Niklas Cassel <nks@...wful.org>