linux-kernel - Re: [PATCH v4] mux: mmio: use reg property when parent device is not a syscon

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Date:   Wed, 25 Oct 2023 07:45:12 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Andrew Davis <afd@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mux: mmio: use reg property when parent device is not
 a syscon

Hi!

2023-10-23 at 18:26, Andrew Davis wrote:
> The DT binding for the reg-mux compatible states it can be used when the
> "parent device of mux controller is not syscon device". It also allows
> for a reg property. When the reg property is provided, use that to
> identify the address space for this mux. If not provided fallback to
> using the parent device as a regmap provider.
> 
> While here use dev_err_probe() in the error path to prevent printing
> a message on probe defer which now can happen in extra ways.
> 
> Signed-off-by: Andrew Davis <afd@...com>
> Reviewed-by: Nishanth Menon <nm@...com>
> ---
> 
> Changes from v3:
>  - Check for probe defer
> 
> Changes from v2:
>  - Rebased on v6.6-rc1
> 
> Changes from v1:
>  - Flip logic as suggested in v1[0]
> 
> [0] https://lore.kernel.org/lkml/1c27d9d4-b1cc-c158-90f7-f7e47e02c424@ti.com/T/
> 
>  drivers/mux/mmio.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mux/mmio.c b/drivers/mux/mmio.c
> index fd1d121a584ba..07c99588ff999 100644
> --- a/drivers/mux/mmio.c
> +++ b/drivers/mux/mmio.c
> @@ -44,14 +44,17 @@ static int mux_mmio_probe(struct platform_device *pdev)
>  	int ret;
>  	int i;
>  
> -	if (of_device_is_compatible(np, "mmio-mux"))
> +	if (of_device_is_compatible(np, "mmio-mux")) {
>  		regmap = syscon_node_to_regmap(np->parent);
> -	else
> -		regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV);
> +	} else {
> +		regmap = device_node_to_regmap(np);
> +		/* Fallback to checking the parent node on any error other than probe defer */
> +		if (IS_ERR(regmap) && regmap != ERR_PTR(-EPROBE_DEFER))
> +			regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV);

I'm not too fond of overly long lines, and the coding style document
agrees with me. Also, please end comments with a period.

		/* Fallback to checking the parent node on "real" errors. */
		if (IS_ERR(regmap) && regmap != ERR_PTR(-EPROBE_DEFER)) {
			regmap = dev_get_regmap(dev->parent, NULL);
			if (!regmap)
				regmap = ERR_PTR(-ENODEV);
		}

> +	}
>  	if (IS_ERR(regmap)) {
>  		ret = PTR_ERR(regmap);
> -		dev_err(dev, "failed to get regmap: %d\n", ret);
> -		return ret;
> +		return dev_err_probe(dev, ret, "failed to get regmap\n");
>  	}

Now that you use dev_err_probe(), please drop the pointless ret
assignment:

 	if (IS_ERR(regmap))
		return dev_err_probe(dev, PTR_ERR(regmap),
				     "failed to get regmap\n");

With those changes, you can add "Acked-by: Peter Rosin <peda@...ntia.se>",
so that Greg can pick it up.

Cheers,
Peter

>  
>  	ret = of_property_count_u32_elems(np, "mux-reg-masks");