linux-kernel - Re: [PATCH E 11/14] OMAP clock: track child clocks

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Date:	Mon, 23 Feb 2009 16:03:49 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"Woodruff, Richard" <r-woodruff2@...com>
Cc:	Paul Walmsley <paul@...an.com>,
	"linux-arm-kernel@...ts.arm.linux.org.uk" 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH E 11/14] OMAP clock: track child clocks

On Thu, Feb 19, 2009 at 06:50:52PM -0600, Woodruff, Richard wrote:
> 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.

It sounds to me like clk_set_parent() needs this then to prevent enabled
clocks being reparented.  By doing so, we no longer need to disable/enable
the clock within the OMAP2/3 set_parent function since we are now
guaranteed that the clock will be disabled.

Ack?

diff --git a/arch/arm/mach-omap2/clock.c b/arch/arm/mach-omap2/clock.c
index 40cb65b..f49bce9 100644
--- 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..b2d9e1f 100644
--- a/arch/arm/plat-omap/clock.c
+++ b/arch/arm/plat-omap/clock.c
@@ -144,12 +144,14 @@ 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);
+		}
 	}
 	spin_unlock_irqrestore(&clockfw_lock, flags);
 
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