diff options
author | Paul Burton <paul.burton@imgtec.com> | 2016-09-08 06:47:29 (GMT) |
---|---|---|
committer | Daniel Schwierzeck <daniel.schwierzeck@gmail.com> | 2016-09-21 13:04:32 (GMT) |
commit | 50fce1d5d874070b058f09e6814c1914e168582d (patch) | |
tree | c4d9d990854ff8ac58ddccdb5ea666fc402717b5 | |
parent | 3f96f87520c22efe4a8b43f45f1b2011da50dc06 (diff) | |
download | u-boot-50fce1d5d874070b058f09e6814c1914e168582d.tar.xz |
serial: ns16550: Support clocks via phandle
Previously ns16550 compatible UARTs probed via device tree have needed
their device tree nodes to contain a clock-frequency property. An
alternative to this commonly used with Linux is to reference a clock via
a phandle. This patch allows U-Boot to support that, retrieving the
clock frequency by probing the appropriate clock device.
For example, a system might choose to provide the UART base clock as a
reference to a clock common to multiple devices:
sys_clk: clock {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <10000000>;
};
uart0: uart@10000000 {
compatible = "ns16550a";
reg = <0x10000000 0x1000>;
clocks = <&sys_clk>;
};
uart1: uart@10000000 {
compatible = "ns16550a";
reg = <0x10001000 0x1000>;
clocks = <&sys_clk>;
};
This removes the need for the frequency information to be duplicated in
multiple nodes and allows the device tree to be more descriptive of the
system.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
-rw-r--r-- | drivers/serial/ns16550.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index 88fca15..3f6ea4d 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -5,6 +5,7 @@ */ #include <common.h> +#include <clk.h> #include <dm.h> #include <errno.h> #include <fdtdec.h> @@ -352,6 +353,8 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev) { struct ns16550_platdata *plat = dev->platdata; fdt_addr_t addr; + struct clk clk; + int err; /* try Processor Local Bus device first */ addr = dev_get_addr(dev); @@ -397,9 +400,21 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev) "reg-offset", 0); plat->reg_shift = fdtdec_get_int(gd->fdt_blob, dev->of_offset, "reg-shift", 0); - plat->clock = fdtdec_get_int(gd->fdt_blob, dev->of_offset, - "clock-frequency", - CONFIG_SYS_NS16550_CLK); + + err = clk_get_by_index(dev, 0, &clk); + if (!err) { + err = clk_get_rate(&clk); + if (!IS_ERR_VALUE(err)) + plat->clock = err; + } else if (err != -ENODEV && err != -ENOSYS) { + debug("ns16550 failed to get clock\n"); + return err; + } + + if (!plat->clock) + plat->clock = fdtdec_get_int(gd->fdt_blob, dev->of_offset, + "clock-frequency", + CONFIG_SYS_NS16550_CLK); if (!plat->clock) { debug("ns16550 clock not defined\n"); return -EINVAL; |