mfd: syscon: Add a DT property to set value width

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>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
index fe8150bb3248e9920f8a24f4b91efe39440b38d6..408f768686f1e9c9606dc5a188cbd7ba1b8f663f 100644 (file)
--- 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 176bf0fa2685e70749f42bad44931b8489e0d681..b7aabeefab07a2b44ab96b3e371de3d731c0b9cf 100644 (file)
--- 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");