[ARM] omap: clk_set_parent: deny changing parent if clock is enabled

Richard Woodruff writes:
| The historic usage of this has been against single use leaf clocks
| (1st instance of gptimer).  When it was used it did:
|       clk_get()
|       clk_set_parent()
|       clk_enable()
|
| This usage was ok for that. Use on a disabled clock is needed.
|
| If there are multiple users on the clock or it is enabled there are
| problems.
|
| The call can still be unfriendly if 2 different drivers are using the
| clock with their own clock get/enable. It might be the function should
| return an error if usecount != 0 to stop surprises.  It is all around
| better if the parenting is done when the clock is off.

This is a good reason to ensure that the clock is not enabled when
clk_set_parent() is called.

Acked-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/mach-omap2/clock.c b/arch/arm/mach-omap2/clock.c
index 40cb65b..f49bce9 100644 (file)
--- a/arch/arm/mach-omap2/clock.c
+++ b/arch/arm/mach-omap2/clock.c
@@ -807,9 +807,6 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
        if (!parent_div)
                return -EINVAL;
 
-       if (clk->usecount > 0)
-               _omap2_clk_disable(clk);
-
        /* Set new source value (previous dividers if any in effect) */
        v = __raw_readl(clk->clksel_reg);
        v &= ~clk->clksel_mask;
@@ -819,9 +816,6 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
 
        _omap2xxx_clk_commit(clk);
 
-       if (clk->usecount > 0)
-               _omap2_clk_enable(clk);
-
        clk_reparent(clk, new_parent);
 
        /* CLKSEL clocks follow their parents' rates, divided by a divisor */

diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c
index 08baa18..2e06145 100644 (file)
--- a/arch/arm/plat-omap/clock.c
+++ b/arch/arm/plat-omap/clock.c
@@ -144,13 +144,16 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
                return ret;
 
        spin_lock_irqsave(&clockfw_lock, flags);
-       if (arch_clock->clk_set_parent)
-               ret = arch_clock->clk_set_parent(clk, parent);
-       if (ret == 0) {
-               if (clk->recalc)
-                       clk->rate = clk->recalc(clk);
-               propagate_rate(clk);
-       }
+       if (clk->usecount == 0) {
+               if (arch_clock->clk_set_parent)
+                       ret = arch_clock->clk_set_parent(clk, parent);
+               if (ret == 0) {
+                       if (clk->recalc)
+                               clk->rate = clk->recalc(clk);
+                       propagate_rate(clk);
+               }
+       } else
+               ret = -EBUSY;
        spin_unlock_irqrestore(&clockfw_lock, flags);
 
        return ret;