clk: sunxi-ng: mux: Add clk notifier functions

On sunxi we support cpufreq by changing the clock rate of PLL-CPU.
It's possible the clock output of the PLL goes out of the CPU's
operational limits when the PLL's multipliers / dividers are changed
and it hasn't stabilized yet. This would result in the CPU hanging.

To circumvent this, we temporarily switch the CPU mux clock to another
stable clock before the rate change, and switch it back after the PLL
stabilizes. This is done with clk notifiers registered on the PLL.

This patch adds common functions for notifiers to reparent mux clocks.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/clk/sunxi-ng/ccu_mux.h b/drivers/clk/sunxi-ng/ccu_mux.h
index 8eab1733eeac..f5123a1a6603 100644
--- a/drivers/clk/sunxi-ng/ccu_mux.h
+++ b/drivers/clk/sunxi-ng/ccu_mux.h
@@ -96,4 +96,18 @@ int ccu_mux_helper_set_parent(struct ccu_common *common,
 			      struct ccu_mux_internal *cm,
 			      u8 index);
 
+struct ccu_mux_nb {
+	struct notifier_block	clk_nb;
+	struct ccu_common	*common;
+	struct ccu_mux_internal	*cm;
+
+	u32	delay_us;	/* How many us to wait after reparenting */
+	u8	bypass_index;	/* Which parent to temporarily use */
+	u8	original_index;	/* This is set by the notifier callback */
+};
+
+#define to_ccu_mux_nb(_nb) container_of(_nb, struct ccu_mux_nb, clk_nb)
+
+int ccu_mux_notifier_register(struct clk *clk, struct ccu_mux_nb *mux_nb);
+
 #endif /* _CCU_MUX_H_ */