Re: [PATCH] mfd: syscon: Restore device_node_to_regmap() for non-syscon nodes

[Daniel Golle <daniel@makrotopia.org>]

On Fri, Jan 24, 2025 at 01:16:44PM -0600, Rob Herring (Arm) wrote:
> Commit ba5095ebbc7a ("mfd: syscon: Allow syscon nodes without a
> "syscon" compatible") broke drivers which call device_node_to_regmap()
> on nodes without a "syscon" compatible. Restore the prior behavior for
> device_node_to_regmap().
> 
> This also makes using device_node_to_regmap() incompatible with
> of_syscon_register_regmap() again, so add kerneldoc for
> device_node_to_regmap() and syscon_node_to_regmap() to make it clear
> how and when each one should be used.
> 
> Fixes: ba5095ebbc7a ("mfd: syscon: Allow syscon nodes without a "syscon" compatible")
> Cc: Will McVicker <willmcvicker@google.com>
> Cc: John Madieu <john.madieu.xa@bp.renesas.com>
> Cc: Nishanth Menon <nm@ti.com>
> Reported-by: Vaishnav Achath <vaishnav.a@ti.com>
> Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
> ---

Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Texted-by: Daniel Golle <daniel@makrotopia.org>

This fix is required to un-break various Mediatek clock drivers as
device_node_to_regmap() is used all over the place there (in
reset.c, clk-gate.c, clk-cpumux.c, clk-mux.c) and commit
3ba5a6159434 ("arm64: dts: mediatek: mt7622: fix clock controllers")
has droped all those unneeded "syscon"s.

>  drivers/mfd/syscon.c | 29 ++++++++++++++++++++++++++---
>  1 file changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 226915ca3c93..aa4a9940b569 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -159,6 +159,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
>  }
>  
>  static struct regmap *device_node_get_regmap(struct device_node *np,
> +					     bool create_regmap,
>  					     bool check_res)
>  {
>  	struct syscon *entry, *syscon = NULL;
> @@ -172,7 +173,7 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
>  		}
>  
>  	if (!syscon) {
> -		if (of_device_is_compatible(np, "syscon"))
> +		if (create_regmap)
>  			syscon = of_syscon_register(np, check_res);
>  		else
>  			syscon = ERR_PTR(-EINVAL);
> @@ -233,15 +234,37 @@ int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap)
>  }
>  EXPORT_SYMBOL_GPL(of_syscon_register_regmap);
>  
> +/**
> + * device_node_to_regmap() - Get or create a regmap for specified device node
> + * @np: Device tree node
> + *
> + * Get a regmap for the specified device node. If there's not an existing
> + * regmap, then one is instantiated. This function should not be used if the
> + * device node has a custom regmap driver or has resources (clocks, resets) to
> + * be managed. Use syscon_node_to_regmap() instead for those cases.
> + *
> + * Return: regmap ptr on success, negative error code on failure.
> + */
>  struct regmap *device_node_to_regmap(struct device_node *np)
>  {
> -	return device_node_get_regmap(np, false);
> +	return device_node_get_regmap(np, true, false);
>  }
>  EXPORT_SYMBOL_GPL(device_node_to_regmap);
>  
> +/**
> + * syscon_node_to_regmap() - Get or create a regmap for specified syscon device node
> + * @np: Device tree node
> + *
> + * Get a regmap for the specified device node. If there's not an existing
> + * regmap, then one is instantiated if the node is a generic "syscon". This
> + * function is safe to use for a syscon registered with
> + * of_syscon_register_regmap().
> + *
> + * Return: regmap ptr on success, negative error code on failure.
> + */
>  struct regmap *syscon_node_to_regmap(struct device_node *np)
>  {
> -	return device_node_get_regmap(np, true);
> +	return device_node_get_regmap(np, of_device_is_compatible(np, "syscon"), true);
>  }
>  EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
>  
> -- 
> 2.45.2
>