This commit intends to implement "fixed-clock" as in Linux. (drivers/clk/clk-fixed-rate.c in Linux)
If you need a very simple clock to just provide fixed clock rate like a crystal oscillator, you do not have to write a new driver. This driver can support it.
Note: As you see in dts/ directories, fixed clocks are often collected in one container node like this:
clocks { refclk_a: refclk_a { #clock-cells = <0>; compatible = "fixed-clock"; clock-frequency = <10000000>; };
refclk_b: refclk_b { #clock-cells = <0>; compatible = "fixed-clock"; clock-frequency = <20000000>; }; };
This does not work in the current DM of U-Boot, unfortunately. The "clocks" node must have 'compatible = "simple-bus";' or something to bind children.
Most of developers would be unhappy about adding such a compatible string only in U-Boot because we generally want to use the same set of device trees beyond projects.
Signed-off-by: Masahiro Yamada yamada.masahiro@socionext.com ---
I do not understand why we need both .get_rate and .get_periph_rate.
I set both in this driver, but I am not sure if I am doing right.
drivers/clk/Makefile | 2 +- drivers/clk/clk-fixed-rate.c | 58 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+), 1 deletion(-) create mode 100644 drivers/clk/clk-fixed-rate.c
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 5fcdf39..75054db 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -5,7 +5,7 @@ # SPDX-License-Identifier: GPL-2.0+ #
-obj-$(CONFIG_CLK) += clk-uclass.o +obj-$(CONFIG_CLK) += clk-uclass.o clk-fixed-rate.o obj-$(CONFIG_$(SPL_)OF_CONTROL) += clk-fdt.o obj-$(CONFIG_ROCKCHIP_RK3036) += clk_rk3036.o obj-$(CONFIG_ROCKCHIP_RK3288) += clk_rk3288.o diff --git a/drivers/clk/clk-fixed-rate.c b/drivers/clk/clk-fixed-rate.c new file mode 100644 index 0000000..048d450 --- /dev/null +++ b/drivers/clk/clk-fixed-rate.c @@ -0,0 +1,58 @@ +/* + * Copyright (C) 2015 Masahiro Yamada yamada.masahiro@socionext.com + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <common.h> +#include <clk.h> +#include <dm/device.h> + +DECLARE_GLOBAL_DATA_PTR; + +struct clk_fixed_rate { + unsigned long fixed_rate; +}; + +#define to_clk_fixed_rate(dev) ((struct clk_fixed_rate *)dev_get_priv(dev)) + +static ulong clk_fixed_get_rate(struct udevice *dev) +{ + return to_clk_fixed_rate(dev)->fixed_rate; +} + +static ulong clk_fixed_get_periph_rate(struct udevice *dev, int ignored) +{ + return to_clk_fixed_rate(dev)->fixed_rate; +} + +const struct clk_ops clk_fixed_rate_ops = { + .get_rate = clk_fixed_get_rate, + .get_periph_rate = clk_fixed_get_periph_rate, + .get_id = clk_get_id_simple, +}; + +static int clk_fixed_rate_probe(struct udevice *dev) +{ + to_clk_fixed_rate(dev)->fixed_rate = + fdtdec_get_int(gd->fdt_blob, dev->of_offset, + "clock-frequency", 0); + + return 0; +} + +static const struct udevice_id clk_fixed_rate_match[] = { + { + .compatible = "fixed-clock", + }, + { /* sentinel */ } +}; + +U_BOOT_DRIVER(clk_fixed_rate) = { + .name = "Fixed Rate Clock", + .id = UCLASS_CLK, + .of_match = clk_fixed_rate_match, + .probe = clk_fixed_rate_probe, + .priv_auto_alloc_size = sizeof(struct clk_fixed_rate), + .ops = &clk_fixed_rate_ops, +};