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Commit 4da37821 authored by Russell King's avatar Russell King Committed by Russell King
Browse files

[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: default avatarRichard Woodruff <r-woodruff2@ti.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 7aec53ac

arch/arm/mach-omap2/clock.c

+0 −6
Original line number Diff line number Diff line
@@ -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 */

arch/arm/plat-omap/clock.c

+10 −7
Original line number Diff line number Diff line
@@ -144,6 +144,7 @@ int clk_set_parent(struct clk *clk, struct clk *parent) 
		return ret;



	spin_lock_irqsave(&clockfw_lock, flags);

	if (clk->usecount == 0) {

		if (arch_clock->clk_set_parent)

			ret = arch_clock->clk_set_parent(clk, parent);

		if (ret == 0) {
@@ -151,6 +152,8 @@ int clk_set_parent(struct clk *clk, struct clk *parent) 
				clk->rate = clk->recalc(clk);

			propagate_rate(clk);

		}

	} else

		ret = -EBUSY;

	spin_unlock_irqrestore(&clockfw_lock, flags);



	return ret;