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Subject: Re: [PATCH v5] mfd: syscon: Add hardware spinlock support
To:     Baolin Wang <baolin.wang@linaro.org>, <lee.jones@linaro.org>,
        <arnd@arndb.de>, <robh+dt@kernel.org>, <mark.rutland@arm.com>
References: <9bd0bfdaf4e869e6216a0ef032b52cd28b33ab16.1512032962.git.baolin.wang@linaro.org>
CC:     <broonie@kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>
From:   Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Message-ID: <78c06786-8bfc-3f15-fdb5-061691010509@mentor.com>
Date:   Thu, 30 Nov 2017 12:38:07 +0200
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On 11/30/2017 11:10 AM, Baolin Wang wrote:
> Some system control registers need hardware spinlock to synchronize
> between the multiple subsystems, so we should add hardware spinlock
> support for syscon.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> Acked-by: Rob Herring <robh@kernel.org>
> ---
> Changes since v4:
>  - Add one exapmle to show how to add hwlock.
>  - Fix the coding style issue.
> 
> Changes since v3:
>  - Add error handling for of_hwspin_lock_get_id()
> 
> Changes since v2:
>  - Add acked tag from Rob.
> 
> Changes since v1:
>  - Remove timeout configuration.
>  - Modify the binding file to add hwlocks.
> ---
>  Documentation/devicetree/bindings/mfd/syscon.txt |    8 ++++++++
>  drivers/mfd/syscon.c                             |   21 +++++++++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
> index 8b92d45..25d9e9c 100644
> --- a/Documentation/devicetree/bindings/mfd/syscon.txt
> +++ b/Documentation/devicetree/bindings/mfd/syscon.txt
> @@ -16,9 +16,17 @@ Required properties:
>  Optional property:
>  - reg-io-width: the size (in bytes) of the IO accesses that should be
>    performed on the device.
> +- hwlocks: reference to a phandle of a hardware spinlock provider node.
>  
>  Examples:
>  gpr: iomuxc-gpr@20e0000 {
>  	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
>  	reg = <0x020e0000 0x38>;
> +	hwlocks = <&hwlock1 1>;
> +};
> +
> +hwlock1: hwspinlock@40500000 {
> +	...
> +	reg = <0x40500000 0x1000>;
> +	#hwlock-cells = <1>;
>  };
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index b93fe4c..5b67dbc 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -13,6 +13,7 @@
>   */
>  
>  #include <linux/err.h>
> +#include <linux/hwspinlock.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/list.h>
> @@ -87,6 +88,26 @@ static struct syscon *of_syscon_register(struct device_node *np)
>  	if (ret)
>  		reg_io_width = 4;
>  
> +	ret = of_hwspin_lock_get_id(np, 0);
> +	if (ret > 0) {
> +		syscon_config.hwlock_id = ret;
> +		syscon_config.hwlock_mode = HWLOCK_IRQSTATE;
> +	} else {
> +		switch (ret) {
> +		case -ENOENT:
> +			/* Ignore missing hwlock, it's optional. */
> +			break;
> +		case 0:
> +			ret = -EINVAL;
> +			/* fall-through */

It breaks the execution on all kernels without CONFIG_HWSPINLOCK enabled.

> +		default:
> +			pr_err("Failed to retrieve valid hwlock: %d\n", ret);
> +			/* fall-through */
> +		case -EPROBE_DEFER:
> +			goto err_regmap;
> +		}
> +	}
> +
>  	syscon_config.reg_stride = reg_io_width;
>  	syscon_config.val_bits = reg_io_width * 8;
>  	syscon_config.max_register = resource_size(&res) - reg_io_width;
> 

--
With best wishes,
Vladimir

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