[PATCH] clk: emit warning if fail to get parent clk

[Jun Nie <jun.nie@linaro.org>]

Emit warning if fail to get parent clk to expose potential issue earlier.
For example, clk_hw_get_rate() will return 0 for a clock without parent core
while parent number is not zero. This cause opp always think it is switching
frequency from 0 to some other frequency. Crash may happen if we switch
from high frequency to low frequency and lower CPU voltage before clk rate
switching.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
---
 drivers/clk/clk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 1a27e99ccb17..78b21b888e56 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -424,6 +424,7 @@ static void clk_core_fill_parent_index(struct clk_core *core, u8 index)
 {
 	struct clk_parent_map *entry = &core->parents[index];
 	struct clk_core *parent = ERR_PTR(-ENOENT);
+	int emit_warn = 0;
 
 	if (entry->hw) {
 		parent = entry->hw->core;
@@ -443,6 +444,12 @@ static void clk_core_fill_parent_index(struct clk_core *core, u8 index)
 	/* Only cache it if it's not an error */
 	if (!IS_ERR(parent))
 		entry->core = parent;
+	else if (parent != ERR_PTR(-EPROBE_DEFER))
+		emit_warn = 1;
+
+	if (emit_warn || (!parent && core->num_parents))
+		pr_warn("Fail to get indexed %d parent for clk %s.",
+			index, core->name);
 }
 
 static struct clk_core *clk_core_get_parent_by_index(struct clk_core *core,
-- 
2.17.1