[PATCH v7 16/22] riscv: Enable cpu clock if it is present

[Pragnesh Patel]

The cpu clock is probably already enabled if we are executing code (though
we could be executing from a different core). This patch prevents the cpu
clock or its parents from being disabled.

Signed-off-by: Sean Anderson <seanga2 at gmail.com>
Signed-off-by: Pragnesh Patel <pragnesh.patel at sifive.com>
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
---
 drivers/cpu/riscv_cpu.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/cpu/riscv_cpu.c b/drivers/cpu/riscv_cpu.c
index 28ad0aa30f..8ebe0341fd 100644
--- a/drivers/cpu/riscv_cpu.c
+++ b/drivers/cpu/riscv_cpu.c
@@ -9,6 +9,7 @@
 #include <errno.h>
 #include <dm/device-internal.h>
 #include <dm/lists.h>
+#include <clk.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -100,6 +101,37 @@ static int riscv_cpu_bind(struct udevice *dev)
 	return 0;
 }
 
+static int riscv_cpu_probe(struct udevice *dev)
+{
+	int ret = 0;
+	u32 clock = 0;
+	struct clk clk;
+
+	/* Get a clock if it exists */
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret)
+		return 0;
+
+	ret = dev_read_u32(dev, "clock-frequency", &clock);
+	if (ret) {
+		debug("clock-frequency not found in dt %d\n", ret);
+		return ret;
+	} else {
+		ret = clk_set_rate(&clk, clock);
+		if (ret < 0) {
+			debug("Could not set CPU clock\n");
+			return ret;
+		}
+	}
+
+	ret = clk_enable(&clk);
+	clk_free(&clk);
+	if (ret == -ENOSYS || ret == -ENOTSUPP)
+		return 0;
+	else
+		return ret;
+}
+
 static const struct cpu_ops riscv_cpu_ops = {
 	.get_desc	= riscv_cpu_get_desc,
 	.get_info	= riscv_cpu_get_info,
@@ -116,6 +148,7 @@ U_BOOT_DRIVER(riscv_cpu) = {
 	.id = UCLASS_CPU,
 	.of_match = riscv_cpu_ids,
 	.bind = riscv_cpu_bind,
+	.probe = riscv_cpu_probe,
 	.ops = &riscv_cpu_ops,
 	.flags = DM_FLAG_PRE_RELOC,
 };
-- 
2.17.1