ENGR00318063-9: clk: do not allow parent switching with another mux being child

When switching parent clock with another basic mux clock being its
child, a glitch might be generated and propagated to downstream clocks
through this child mux.

The patch adds a flag CLK_IS_BASIC_MUX to identify the basic mux clocks,
and prohibit the parent switching when the clock itself is the parent of
any basic mux clock.  With this check, the parent switching of a clock
has to happen before the child mux switches to this clock path.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 4e9f36a15033..0c71babde4a7 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -28,6 +28,12 @@
 #define CLK_IS_BASIC		BIT(5) /* Basic clk, can't do a to_clk_foo() */
 #define CLK_GET_RATE_NOCACHE	BIT(6) /* do not use the cached clk rate */
 #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */
+/*
+ * Basic mux clk, can't switch parent while there is another basic mux clk
+ * being its child.  Otherwise, a glitch might be propagated to downstream
+ * clocks through this child mux.
+ */
+#define CLK_IS_BASIC_MUX	BIT(8)
 
 struct clk_hw;