[PATCH v10 18/21] riscv: Enable cpu clock if it is present

[Sean Anderson <seanga2@gmail.com>]

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@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
---
This patch was previously submitted on its own as
https://patchwork.ozlabs.org/patch/1232420/

Changes in v4:
- New

 drivers/cpu/riscv_cpu.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/cpu/riscv_cpu.c b/drivers/cpu/riscv_cpu.c
index c6ed060abc..9ce58695aa 100644
--- a/drivers/cpu/riscv_cpu.c
+++ b/drivers/cpu/riscv_cpu.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
+ * Copyright (C) 2020, Sean Anderson <seanga2@gmail.com>
  */
 
 #include <clk.h>
@@ -117,6 +118,24 @@ static int riscv_cpu_bind(struct udevice *dev)
 	return 0;
 }
 
+static int riscv_cpu_probe(struct udevice *dev)
+{
+	int ret = 0;
+	struct clk clk;
+
+	/* Get a clock if it exists */
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret)
+		return 0;
+
+	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,
@@ -133,6 +152,7 @@ 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,
 };
-- 
2.26.2