linux-kernel - Re: [RFC PATCH v3 2/2] mfd: syscon: allow reset control for syscon devices

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Date:   Wed, 4 Jan 2023 16:54:53 +0000
From:   Lee Jones <lee@...nel.org>
To:     Jeremy Kerr <jk@...econstruct.com.au>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [RFC PATCH v3 2/2] mfd: syscon: allow reset control for syscon
 devices

On Sun, 11 Dec 2022, Jeremy Kerr wrote:

> Simple syscon devices may require deassertion of a reset signal in order
> to access their register set. Rather than requiring a custom driver to
> implement this, we can use the generic "resets" specifiers to link a
> reset line to the syscon.
> 
> This change adds an optional reset line to the syscon device
> description, and deasserts the reset if detected.
> 
> Signed-off-by: Jeremy Kerr <jk@...econstruct.com.au>
> 
> ---
> v2:
>  * do reset control in the early of_syscon_register() path, rather than
>    the platform device init, which isn't used.
> v3:
>  * use a direct reset_control_deassert rather than handling in the
>    regmap
> ---
>  drivers/mfd/syscon.c | 27 +++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index bdb2ce7ff03b..05e286a69dbe 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -20,6 +20,7 @@
>  #include <linux/platform_data/syscon.h>
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
> +#include <linux/reset.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/slab.h>
>  
> @@ -31,6 +32,7 @@ static LIST_HEAD(syscon_list);
>  struct syscon {
>  	struct device_node *np;
>  	struct regmap *regmap;
> +	struct reset_control *reset;
>  	struct list_head list;
>  };
>  
> @@ -40,7 +42,7 @@ static const struct regmap_config syscon_regmap_config = {
>  	.reg_stride = 4,
>  };
>  
> -static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
> +static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
>  {
>  	struct clk *clk;
>  	struct syscon *syscon;
> @@ -50,6 +52,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  	int ret;
>  	struct regmap_config syscon_config = syscon_regmap_config;
>  	struct resource res;
> +	struct reset_control *reset;
>  
>  	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
>  	if (!syscon)
> @@ -114,7 +117,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  		goto err_regmap;
>  	}
>  
> -	if (check_clk) {
> +	if (check_res) {
>  		clk = of_clk_get(np, 0);
>  		if (IS_ERR(clk)) {
>  			ret = PTR_ERR(clk);
> @@ -124,7 +127,17 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  		} else {
>  			ret = regmap_mmio_attach_clk(regmap, clk);
>  			if (ret)
> -				goto err_attach;
> +				goto err_attach_clk;
> +		}
> +
> +		reset = of_reset_control_get_optional_exclusive(np, NULL);
> +		if (IS_ERR(reset)) {
> +			ret = PTR_ERR(reset);
> +			goto err_attach_clk;
> +		} else {
> +			ret = reset_control_deassert(reset);
> +			if (ret)
> +				goto err_reset;
>  		}

The else is superfluous, right?

Arnd, besides this are you happy with the patch?

-- 
Lee Jones [李琼斯]