clk: boston: Providea simple driver for Boston board clocks

Add a simple driver for the clocks provided by the MIPS Boston
development board. The system provides information about 2 clocks whose
rates are fixed by the bitfile flashed in the boards FPGA, and this
driver simply reads the rates of these 2 clocks.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/clk/Kconfig

@@ -20,6 +20,14 @@ config SPL_CLK
 	  setting up clocks within SPL, and allows the same drivers to be
 	  used as U-Boot proper.
 
+config CLK_BOSTON
+	def_bool y if TARGET_BOSTON
+	depends on CLK
+	select REGMAP
+	select SYSCON
+	help
+	  Enable this to support the clocks
+
 source "drivers/clk/tegra/Kconfig"
 source "drivers/clk/uniphier/Kconfig"
 source "drivers/clk/exynos/Kconfig"

drivers/clk/Makefile

@@ -15,3 +15,4 @@ obj-y += tegra/
 obj-$(CONFIG_CLK_UNIPHIER) += uniphier/
 obj-$(CONFIG_CLK_EXYNOS) += exynos/
 obj-$(CONFIG_CLK_AT91) += at91/
+obj-$(CONFIG_CLK_BOSTON) += clk_boston.o

drivers/clk/clk_boston.c

+/*
+ * Copyright (C) 2016 Imagination Technologies
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm.h>
+#include <dt-bindings/clock/boston-clock.h>
+#include <regmap.h>
+#include <syscon.h>
+
+struct clk_boston {
+	struct regmap *regmap;
+};
+
+#define BOSTON_PLAT_MMCMDIV		0x30
+# define BOSTON_PLAT_MMCMDIV_CLK0DIV	(0xff << 0)
+# define BOSTON_PLAT_MMCMDIV_INPUT	(0xff << 8)
+# define BOSTON_PLAT_MMCMDIV_MUL	(0xff << 16)
+# define BOSTON_PLAT_MMCMDIV_CLK1DIV	(0xff << 24)
+
+static uint32_t ext_field(uint32_t val, uint32_t mask)
+{
+	return (val & mask) >> (ffs(mask) - 1);
+}
+
+static ulong clk_boston_get_rate(struct clk *clk)
+{
+	struct clk_boston *state = dev_get_platdata(clk->dev);
+	uint32_t in_rate, mul, div;
+	uint mmcmdiv;
+	int err;
+
+	err = regmap_read(state->regmap, BOSTON_PLAT_MMCMDIV, &mmcmdiv);
+	if (err)
+		return 0;
+
+	in_rate = ext_field(mmcmdiv, BOSTON_PLAT_MMCMDIV_INPUT);
+	mul = ext_field(mmcmdiv, BOSTON_PLAT_MMCMDIV_MUL);
+
+	switch (clk->id) {
+	case BOSTON_CLK_SYS:
+		div = ext_field(mmcmdiv, BOSTON_PLAT_MMCMDIV_CLK0DIV);
+		break;
+	case BOSTON_CLK_CPU:
+		div = ext_field(mmcmdiv, BOSTON_PLAT_MMCMDIV_CLK1DIV);
+		break;
+	default:
+		return 0;
+	}
+
+	return (in_rate * mul * 1000000) / div;
+}
+
+const struct clk_ops clk_boston_ops = {
+	.get_rate = clk_boston_get_rate,
+};
+
+static int clk_boston_ofdata_to_platdata(struct udevice *dev)
+{
+	struct clk_boston *state = dev_get_platdata(dev);
+	struct udevice *syscon;
+	int err;
+
+	err = uclass_get_device_by_phandle(UCLASS_SYSCON, dev,
+					   "regmap", &syscon);
+	if (err) {
+		error("unable to find syscon device\n");
+		return err;
+	}
+
+	state->regmap = syscon_get_regmap(syscon);
+	if (!state->regmap) {
+		error("unable to find regmap\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static const struct udevice_id clk_boston_match[] = {
+	{
+		.compatible = "img,boston-clock",
+	},
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(clk_boston) = {
+	.name = "boston_clock",
+	.id = UCLASS_CLK,
+	.of_match = clk_boston_match,
+	.ofdata_to_platdata = clk_boston_ofdata_to_platdata,
+	.platdata_auto_alloc_size = sizeof(struct clk_boston),
+	.ops = &clk_boston_ops,
+};

include/dt-bindings/clock/boston-clock.h

+/*
+ * Copyright (C) 2016 Imagination Technologies
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#ifndef __DT_BINDINGS_CLOCK_BOSTON_CLOCK_H__
+#define __DT_BINDINGS_CLOCK_BOSTON_CLOCK_H__
+
+#define BOSTON_CLK_SYS 0
+#define BOSTON_CLK_CPU 1
+
+#endif /* __DT_BINDINGS_CLOCK_BOSTON_CLOCK_H__ */