[PATCH v2] clk: check parent_name in clk_register to avoid confusing log_error() output

[Yang Xiwen via B4 Relay]

From: Yang Xiwen <forbidden405 at outlook.com>

For some gate clocks and fixed clocks without a parent, calling
clk_register will print an useless error message indicating that parent
is missing. Fix that by gaurding log_xxx() with an if-statement.

Signed-off-by: Yang Xiwen <forbidden405 at outlook.com>
Suggested-by: Sean Anderson <seanga2 at gmail.com>
---
It's found during my development for HiSilicon clock driver.
---
Changes in v2:
- drop the commit which exports clk_mux_register.
- drop the commit which is already merged
- drop ccf enable_count fix as it'll be in another patchset
- use Anderson's patch for clk_register()
- Link to v1: https://lore.kernel.org/r/20230809-clk-fix-v1-0-808dbae54e5e@outlook.com
---
 drivers/clk/clk.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a5a3461b66..6ede1b4d4d 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -18,17 +18,19 @@
 int clk_register(struct clk *clk, const char *drv_name,
 		 const char *name, const char *parent_name)
 {
-	struct udevice *parent;
+	struct udevice *parent = NULL;
 	struct driver *drv;
 	int ret;
 
-	ret = uclass_get_device_by_name(UCLASS_CLK, parent_name, &parent);
-	if (ret) {
-		log_err("%s: failed to get %s device (parent of %s)\n",
-			__func__, parent_name, name);
-	} else {
-		log_debug("%s: name: %s parent: %s [0x%p]\n", __func__, name,
-			  parent->name, parent);
+	if (parent_name) {
+		ret = uclass_get_device_by_name(UCLASS_CLK, parent_name, &parent);
+		if (ret) {
+			log_err("%s: failed to get %s device (parent of %s)\n",
+				__func__, parent_name, name);
+		} else {
+			log_debug("%s: name: %s parent: %s [0x%p]\n", __func__, name,
+				  parent->name, parent);
+		}
 	}
 
 	drv = lists_driver_lookup_name(drv_name);

---
base-commit: 580eb31199be8a822e62f20965854a242f895d03
change-id: 20230807-clk-fix-17e895f79817

Best regards,
-- 
Yang Xiwen <forbidden405 at outlook.com>