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.masah...@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.masah...@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,
+};
--
1.9.1
_______________________________________________
U-Boot mailing list
U-Boot@lists.denx.de
http://lists.denx.de/mailman/listinfo/u-boot
