[PATCH v3 2/5] mfd: syscon: add a DT property to set value width
From: Lee Jones <hidden>
Date: 2015-11-17 09:19:58
Also in:
linux-watchdog, lkml
On Mon, 16 Nov 2015, Damien Riegel wrote:
quoted hunk ↗ jump to hunk
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 "bus-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 adjust the register stride to bus-width / 8. If not provided, the default configuration is used. Signed-off-by: Damien Riegel <redacted> --- Documentation/devicetree/bindings/mfd/syscon.txt | 3 +++ drivers/mfd/syscon.c | 12 ++++++++++++ 2 files changed, 15 insertions(+)diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt index fe8150b..4c9d187 100644 --- a/Documentation/devicetree/bindings/mfd/syscon.txt +++ b/Documentation/devicetree/bindings/mfd/syscon.txt@@ -13,6 +13,9 @@ Required properties: - compatible: Should contain "syscon". - reg: the register region can be accessed from syscon +Optional property: +- bus-width: width of the data bus. Can be <8>, <16>, <32>, or <64>. + Examples: gpr: iomuxc-gpr at 020e0000 { compatible = "fsl,imx6q-iomuxc-gpr", "syscon";diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index 176bf0f..00b0995 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 bus_width; int ret; struct regmap_config syscon_config = syscon_regmap_config;@@ -69,6 +70,17 @@ 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; + ret = of_property_read_u32(np, "bus-width", &bus_width); + if (!ret) {
This syntax is confusing, as we normally associate it with an error condition. Instead, I'd use: if (of_property_read_u32(np, "bus-width", &bus_width) == 0) Or, for more clarity: of_property_read_u32(np, "bus-width", &bus_width); if (bus_width) If you choose this version (which I think is my preferred method, don't forget to initialise 'bus_width' to zero.
+ /*
+ * the property has been provided, regmap_init_mmio
+ * will return an error if these values are invalid
+ * so there is no need to check them here.
+ */
+ syscon_config.val_bits = bus_width;
+ syscon_config.reg_stride = syscon_config.val_bits / 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 Follow Linaro: Facebook | Twitter | Blog