FROMLIST: clk: adjust clocks to their requested rate after parent changes

Given a hirarchy of clk1 -> [div] -> clk2, when the rate of clk1 gets
changed, clk2 changes as well as the divider stays the same. There may
be cases where a user of clk2 needs it at a specific rate, so clk2
needs to be readjusted for the changed rate of clk1.

So if a rate was requested for the clock, and its rate changed during
the underlying rate-change, with this change the clock framework now
tries to readjust the rate back to/near the requested one.

The whole process is protected by a new clock-flag to not force this
behaviour change onto every clock defined in the ccf.

(am from https://patchwork.kernel.org/patch/8993761/)

Change-Id: Ie2636710cb4e66815ee45b28ec86eeaaa47c55c7
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f66af1ccdb9f13ff6c735d35e98f95dd5f04bd13..ba7d8e3e3db58035b2a199b189a94a6277fbf6df 100644 (file)
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1423,6 +1423,9 @@ static struct clk_core *clk_propagate_rate_change(struct clk_core *core,
        return fail_clk;
 }
 
+static int clk_core_set_rate_nolock(struct clk_core *core,
+                                   unsigned long req_rate);
+
 /*
  * walk down a subtree and set the new rates notifying the rate
  * change on the way
@@ -1507,6 +1510,12 @@ static void clk_change_rate(struct clk_core *core)
        /* handle the new child who might not be in core->children yet */
        if (core->new_child)
                clk_change_rate(core->new_child);
+
+       /* handle a changed clock that needs to readjust its rate */
+       if (core->flags & CLK_KEEP_REQ_RATE && core->req_rate
+                                           && core->new_rate != old_rate
+                                           && core->new_rate != core->req_rate)
+               clk_core_set_rate_nolock(core, core->req_rate);
 }
 
 static int clk_core_set_rate_nolock(struct clk_core *core,
@@ -1542,11 +1551,11 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
                return -EBUSY;
        }
 
+       core->req_rate = req_rate;
+
        /* change the rates */
        clk_change_rate(top);
 
-       core->req_rate = req_rate;
-
        return ret;
 }
 

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 375cdb9d1e53bf25e75432d2de00b75816aafbec..2c139f90e4a27a5e8f4e996abd2a7693c28a720a 100644 (file)
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -32,6 +32,7 @@
 #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */
 #define CLK_RECALC_NEW_RATES   BIT(9) /* recalc rates after notifications */
 #define CLK_SET_RATE_UNGATE    BIT(10) /* clock needs to run to set rate */
+#define CLK_KEEP_REQ_RATE      BIT(12) /* keep reqrate on parent rate change */
 
 struct clk;
 struct clk_hw;