Date: Mon, 7 Dec 2015 09:40:20 +0000
From: Lee Jones <lee.jones@linaro.org>
To: Damien Riegel <damien.riegel@savoirfairelinux.com>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        Russell King <linux@arm.linux.org.uk>, Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <kernel@pengutronix.de>, Arnd Bergmann <arnd@arndb.de>,
        Samuel Ortiz <sameo@linux.intel.com>, Wim Van Sebroeck <wim@iguana.be>,
        Guenter Roeck <linux@roeck-us.net>, kernel@savoirfairelinux.com
Subject: Re: [PATCH v7 2/6] mfd: syscon: add a DT property to set value width
Message-ID: <20151207094020.GF3384@x1>
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On Mon, 30 Nov 2015, Damien Riegel wrote:

> Currently syscon has a fixed configuration of 32 bits for register and
> values widths. In some cases, it would be desirable to be able to
> customize the value width.
> 
> For example, certain boards (like the ones manufactured by Technologic
> Systems) have a FPGA that is memory-mapped, but its registers are only
> 16-bit wide.
> 
> This patch adds an optional "reg-io-width" DT binding for syscon that
> allows to change the width for the data bus (i.e. val_bits). If this
> property is provided, it will also set the register stride to
> reg-io-width's value. If not provided, the default configuration is
> used.
> 
> Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
> ---
>  Documentation/devicetree/bindings/mfd/syscon.txt |  4 ++++
>  drivers/mfd/syscon.c                             | 13 +++++++++++++
>  2 files changed, 17 insertions(+)

Applied, thanks.

> diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
> index fe8150b..408f768 100644
> --- a/Documentation/devicetree/bindings/mfd/syscon.txt
> +++ b/Documentation/devicetree/bindings/mfd/syscon.txt
> @@ -13,6 +13,10 @@ Required properties:
>  - compatible: Should contain "syscon".
>  - reg: the register region can be accessed from syscon
>  
> +Optional property:
> +- reg-io-width: the size (in bytes) of the IO accesses that should be
> +  performed on the device.
> +
>  Examples:
>  gpr: iomuxc-gpr@020e0000 {
>  	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 176bf0f..b7aabee 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -47,6 +47,7 @@ static struct syscon *of_syscon_register(struct device_node *np)
>  	struct syscon *syscon;
>  	struct regmap *regmap;
>  	void __iomem *base;
> +	u32 reg_io_width;
>  	int ret;
>  	struct regmap_config syscon_config = syscon_regmap_config;
>  
> @@ -69,6 +70,18 @@ static struct syscon *of_syscon_register(struct device_node *np)
>  	 else if (of_property_read_bool(np, "little-endian"))
>  		syscon_config.val_format_endian = REGMAP_ENDIAN_LITTLE;
>  
> +	/*
> +	 * search for reg-io-width property in DT. If it is not provided,
> +	 * default to 4 bytes. regmap_init_mmio will return an error if values
> +	 * are invalid so there is no need to check them here.
> +	 */
> +	ret = of_property_read_u32(np, "reg-io-width", &reg_io_width);
> +	if (ret)
> +		reg_io_width = 4;
> +
> +	syscon_config.reg_stride = reg_io_width;
> +	syscon_config.val_bits = reg_io_width * 8;
> +
>  	regmap = regmap_init_mmio(NULL, base, &syscon_config);
>  	if (IS_ERR(regmap)) {
>  		pr_err("regmap init failed\n");

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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