clk: propagate parent change up one level

This patch adds support for propagation of setup of clock's parent one level
up.

This feature is helpful when a driver changes topology of its clocks using
clk_set_parent().  The problem occurs when on one platform/SoC driver's clock
is located at MUX output but on the other platform/SoC there is a gated proxy
clock between the MUX and driver's clock.  In such a case, driver's code has to
be modified to use one clock for enabling and the other clock for setup of a
parent.

The code updates are avoided by propagating setup of a parent up one level.

Additionally, this patch adds CLK_SET_PARENT_PARENT (sorry for naming) flag to
inform clk-core that clk_set_parent() should be propagated.

Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Change-Id: I206d23fb86cc09bce943ef9971a710876e3a7744

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a9abf1b..ba2f31b 100644 (file)
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1506,6 +1506,12 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 
        /* try finding the new parent index */
        if (parent) {
+               if ((clk->flags & CLK_SET_PARENT_PARENT)
+                   && clk->num_parents == 1) {
+                       ret = clk_set_parent(clk->parent, parent);
+                       goto out;
+               }
+
                p_index = clk_fetch_parent_index(clk, parent);
                p_rate = parent->rate;
                if (p_index == clk->num_parents) {

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 1186098..061052f 100644 (file)
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -27,6 +27,7 @@
 #define CLK_IS_ROOT            BIT(4) /* root clk, has no parent */
 #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_PARENT_PARENT  BIT(7) /* propagate parent change up one level */
 
 struct clk_hw;